1.
Photography
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Typically, a lens is used to focus the light reflected or emitted from objects into a real image on the light-sensitive surface inside a camera during a timed exposure. With an electronic sensor, this produces an electrical charge at each pixel. A negative image on film is used to photographically create a positive image on a paper base, known as a print. The word photography was created from the Greek roots φωτός, genitive of φῶς, light and γραφή representation by means of lines or drawing, several people may have coined the same new term from these roots independently. Johann von Maedler, a Berlin astronomer, is credited in a 1932 German history of photography as having used it in an article published on 25 February 1839 in the German newspaper Vossische Zeitung. Both of these claims are now widely reported but apparently neither has ever been confirmed as beyond reasonable doubt. Credit has traditionally given to Sir John Herschel both for coining the word and for introducing it to the public. Photography is the result of combining several technical discoveries, later Greek mathematicians Aristotle and Euclid also independently described a pinhole camera in the 5th and 4th centuries BCE. Daniele Barbaro described a diaphragm in 1566, wilhelm Homberg described how light darkened some chemicals in 1694. The fiction book Giphantie, published in 1760, by French author Tiphaigne de la Roche, the discovery of the camera obscura that provides an image of a scene dates back to ancient China. Leonardo da Vinci mentions natural camera obscura that are formed by dark caves on the edge of a sunlit valley, a hole in the cave wall will act as a pinhole camera and project a laterally reversed, upside down image on a piece of paper. So the birth of photography was primarily concerned with inventing means to capture, renaissance painters used the camera obscura which, in fact, gives the optical rendering in color that dominates Western Art. The camera obscura literally means dark chamber in Latin and it is a box with a hole in it which allows light to go through and create an image onto the piece of paper. Around the year 1800, British inventor Thomas Wedgwood made the first known attempt to capture the image in a camera obscura by means of a light-sensitive substance and he used paper or white leather treated with silver nitrate. The shadow images eventually darkened all over, the first permanent photoetching was an image produced in 1822 by the French inventor Nicéphore Niépce, but it was destroyed in a later attempt to make prints from it. Niépce was successful again in 1825, in 1826 or 1827, he made the View from the Window at Le Gras, the earliest surviving photograph from nature. Because Niépces camera photographs required a long exposure, he sought to greatly improve his bitumen process or replace it with one that was more practical. With an eye to eventual commercial exploitation, the partners opted for total secrecy, Daguerres efforts culminated in what would later be named the daguerreotype process
2.
Heliography
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Heliography is the photographic process invented by Joseph Nicéphore Niépce around 1822, which he used to make the earliest known surviving photograph from nature, View from the Window at Le Gras. The process used Bitumen of Judea, a naturally occurring asphalt and it hardened in proportion to its exposure to light. When the plate was washed with oil of lavender, only the areas remained. The word has also used to refer to other phenomena, for description of the sun, for photography in general, for signalling by heliograph. Found on old reproductions, may stand for the French word héliogravure, Art & Architecture Thesaurus, s. v. heliography. The University of Texas at Austin, an Improved Method in the Art of Signalling for Military & Scientific Purposes
3.
View from the Window at Le Gras
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View from the Window at Le Gras is a heliographic image and the oldest surviving camera photograph. It was created by Nicéphore Niépce in 1826 or 1827 at Saint-Loup-de-Varennes, France, Niépce captured the scene with a camera obscura focused onto a 16.2 cm ×20.2 cm pewter plate thinly coated with Bitumen of Judea, a naturally occurring asphalt. The bitumen hardened in the brightly lit areas, but in the dimly lit areas it remained soluble and could be washed away with a mixture of oil of lavender, a very long exposure in the camera was required. Sunlight strikes the buildings on opposite sides, suggesting an exposure that lasted eight hours. A researcher who studied Niépces notes and recreated his processes found that the exposure must have continued for several days, in late 1827, Niépce visited England. He showed this and several specimens of his work to botanical illustrator Francis Bauer. View from the Window at Le Gras was the example of a camera photograph. Bauer encouraged him to present his heliography process to the Royal Society, before returning to France, Niépce gave his paper and the specimens to Bauer. Niépce died suddenly in 1833, due to a stroke, on March 9,1839, the specimens were finally exhibited at the Royal Society. After Bauers death in 1840 they passed through several hands and were exhibited as historical curiosities. View from the Window at Le Gras was last seen in 1905, historian Helmut Gernsheim tracked down the photograph in 1952 and brought it to prominence, reinforcing the claim that Niépce is the inventor of photography. Gernsheim heavily retouched one of the prints to clean it up and make the scene more comprehensible. During the 1950s and early 1960s, Gernsheim lent the photograph to several exhibitions in continental Europe, in 1963, Harry Ransom purchased most of Gernsheims photography collection for the University of Texas at Austin. The Niépce heliograph was not included in the sale, but shortly afterward Gernsheim donated it, although it has rarely traveled since then, in 2012–13 it visited Mannheim, Germany, as part of an exhibition entitled The Birth of Photography—Highlights of the Helmut Gernsheim Collection. It is normally on display in the lobby of the Harry Ransom Humanities Research Center in Austin. They confirmed that the image consists of bitumen and that the plate is pewter. The Institute also designed and built the elaborate display case system that now houses the artifact in a continuously monitored, stabilized, in 2007, scientists from the Louvre Museum published an analysis of the photograph using ion beam analysis, with data taken on their 2 MV electrostatic accelerator. This showed the details of the process that was corroding the image
4.
Camera obscura
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The surroundings of the projected image have to be relatively dark for the image to be clear, so many historical camera obscura experiments were performed in dark rooms. The term camera obscura also refers to constructions or devices that use of the principle within a box. Camerae obscurae with a lens in the opening have been used since the second half of the 16th century, before the term camera obscura was first used in 1604, many other expressions were used including cubiculum obscurum, cubiculum tenebricosum, conclave obscurum and locus obscurus. Rays of light travel in straight lines and change when they are reflected and partly absorbed by an object, retaining information about the color, lit objects reflect rays of light in all directions. The human eye itself works much like a camera obscura with an opening, a biconvex lens, a camera obscura device consists of a box, tent or room with a small hole in one side. Light from a scene passes through the hole and strikes a surface inside, where the scene is reproduced, inverted and reversed. The image can be projected onto paper, and can then be traced to produce an accurate representation. In order to produce a reasonably clear projected image, the aperture has to be about 1/100th the distance to the screen, many camerae obscurae use a lens rather than a pinhole because it allows a larger aperture, giving a usable brightness while maintaining focus. As the pinhole is made smaller, the image gets sharper, with too small a pinhole, however, the sharpness worsens, due to diffraction. Using mirrors, as in an 18th-century overhead version, it is possible to project a right-side-up image, another more portable type is a box with an angled mirror projecting onto tracing paper placed on the glass top, the image being upright as viewed from the back. There are theories that occurrences of camera obscura effects inspired paleolithic cave paintings and it is also suggested that camera obscura projections could have played a role in Neolithic structures. Perforated gnomons projecting an image of the sun were described in the Chinese Zhoubi Suanjing writings. The location of the circle can be measured to tell the time of day. In Arab and European cultures its invention was later attributed to Egyptian astronomer. Some ancient sightings of gods and spirits, especially in worship, are thought to possibly have been conjured up by means of camera obscura projections. In these writings it is explained how the image in a collecting-point or treasure house is inverted by an intersecting point that collected the light. Light coming from the foot of a person would partly be hidden below. Rays from the head would partly be hidden above and partly form the part of the image
5.
Image
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Images may be two-dimensional, such as a photograph or screen display, or three-dimensional, such as a statue or hologram. They may be captured by optical devices – such as cameras, mirrors, lenses, telescopes, microscopes, etc. and natural objects and phenomena, such as the human eye or water. The word image is used in the broader sense of any two-dimensional figure such as a map, a graph. A volatile image is one that only for a short period of time. This may be a reflection of an object by a mirror, a fixed image, also called a hard copy, is one that has been recorded on a material object, such as paper or textile by photography or any other digital process. A mental image exists in a mind, as something one remembers or imagines. The subject of an image need not be real, it may be a concept, such as a graph, function. For example, Sigmund Freud claimed to have dreamed purely in aural-images of dialogs, a still image is a single static image, as distinguished from a kinetic image. This phrase is used in photography, visual media and the industry to emphasize that one is not talking about movies. A film still is a taken on the set of a movie or television program during production. In literature, imagery is a picture which appeals to the senses. It can both be figurative and literal, a moving image is typically a movie or video, including digital video. It could also be an animated display such as a zoetrope, library of Congress – Format Descriptions for Still Images Image Processing – Online Open Research Group Legal Issues Regarding Images Image Copyright Case
6.
Light
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Light is electromagnetic radiation within a certain portion of the electromagnetic spectrum. The word usually refers to light, which is visible to the human eye and is responsible for the sense of sight. Visible light is defined as having wavelengths in the range of 400–700 nanometres, or 4.00 × 10−7 to 7.00 × 10−7 m. This wavelength means a range of roughly 430–750 terahertz. The main source of light on Earth is the Sun, sunlight provides the energy that green plants use to create sugars mostly in the form of starches, which release energy into the living things that digest them. This process of photosynthesis provides virtually all the used by living things. Historically, another important source of light for humans has been fire, with the development of electric lights and power systems, electric lighting has effectively replaced firelight. Some species of animals generate their own light, a process called bioluminescence, for example, fireflies use light to locate mates, and vampire squids use it to hide themselves from prey. Visible light, as all types of electromagnetic radiation, is experimentally found to always move at this speed in a vacuum. In physics, the term sometimes refers to electromagnetic radiation of any wavelength. In this sense, gamma rays, X-rays, microwaves and radio waves are also light, like all types of light, visible light is emitted and absorbed in tiny packets called photons and exhibits properties of both waves and particles. This property is referred to as the wave–particle duality, the study of light, known as optics, is an important research area in modern physics. Generally, EM radiation, or EMR, is classified by wavelength into radio, microwave, infrared, the behavior of EMR depends on its wavelength. Higher frequencies have shorter wavelengths, and lower frequencies have longer wavelengths, when EMR interacts with single atoms and molecules, its behavior depends on the amount of energy per quantum it carries. There exist animals that are sensitive to various types of infrared, infrared sensing in snakes depends on a kind of natural thermal imaging, in which tiny packets of cellular water are raised in temperature by the infrared radiation. EMR in this range causes molecular vibration and heating effects, which is how these animals detect it, above the range of visible light, ultraviolet light becomes invisible to humans, mostly because it is absorbed by the cornea below 360 nanometers and the internal lens below 400. Furthermore, the rods and cones located in the retina of the eye cannot detect the very short ultraviolet wavelengths and are in fact damaged by ultraviolet. Many animals with eyes that do not require lenses are able to detect ultraviolet, by quantum photon-absorption mechanisms, various sources define visible light as narrowly as 420 to 680 to as broadly as 380 to 800 nm
7.
Photographic film
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This article is mainly concerned with still photography film. For motion picture film, please see film stock, photographic film is a strip or sheet of transparent plastic film base coated on one side with a gelatin emulsion containing microscopically small light-sensitive silver halide crystals. The sizes and other characteristics of the crystals determine the sensitivity, contrast, the emulsion will gradually darken if left exposed to light, but the process is too slow and incomplete to be of any practical use. Instead, a short exposure to the image formed by a camera lens is used to produce only a very slight chemical change. This creates an invisible latent image in the emulsion, which can be developed into a visible photograph. In addition to light, all films are sensitive to ultraviolet, X-rays. Unmodified silver halide crystals are only to the blue part of the visible spectrum. This problem was overcome with the discovery that certain dyes, called sensitizing dyes, first orthochromatic and finally panchromatic films were developed. Panchromatic film renders all colors in shades of gray approximately matching their subjective brightness, by similar techniques special-purpose films can be made sensitive to the infrared region of the spectrum. In black-and-white photographic film there is one layer of silver halide crystals. When the exposed silver halide grains are developed, the silver halide crystals are converted to metallic silver, color film has at least three sensitive layers, incorporating different combinations of sensitizing dyes. Typically the blue-sensitive layer is on top, followed by a filter layer to stop any remaining blue light from affecting the layers below. Next come a green-and-blue sensitive layer, and a sensitive layer. During development, the silver halide crystals are converted to metallic silver. Because the by-products are created in direct proportion to the amount of exposure and development, following development, the silver is converted back to silver halide crystals in the bleach step. It is removed from the film during the process of fixing the image on the film with a solution of ammonium thiosulfate or sodium thiosulfate, fixing leaves behind only the formed color dyes, which combine to make up the colored visible image. Later color films, like Kodacolor II, have as many as 12 emulsion layers, the earliest practical photographic process, the daguerreotype, introduced in 1839, did not use film. The light-sensitive chemicals were formed on the surface of a copper sheet
8.
Charge-coupled device
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A charge-coupled device is a device for the movement of electrical charge, usually from within the device to an area where the charge can be manipulated, for example conversion into a digital value. This is achieved by shifting the signals between stages within the one at a time. CCDs move charge between capacitive bins in the device, with the shift allowing for the transfer of charge between bins, in recent years CCD has become a major technology for digital imaging. In a CCD image sensor, pixels are represented by p-doped metal-oxide-semiconductors capacitors, the charge-coupled device was invented in 1969 at AT&T Bell Labs by Willard Boyle and George E. Smith. The lab was working on bubble memory when Boyle and Smith conceived of the design of what they termed, in their notebook. The device could be used as a shift register, the essence of the design was the ability to transfer charge along the surface of a semiconductor from one storage capacitor to the next. The concept was similar in principle to the device, which was developed at Philips Research Labs during the late 1960s. The first patent on the application of CCDs to imaging was assigned to Michael Tompsett, the initial paper describing the concept listed possible uses as a memory, a delay line, and an imaging device. The first experimental device demonstrating the principle was a row of closely spaced metal squares on a silicon surface electrically accessed by wire bonds. The first working CCD made with integrated circuit technology was a simple 8-bit shift register and this device had input and output circuits and was used to demonstrate its use as a shift register and as a crude eight pixel linear imaging device. Development of the device progressed at a rapid rate, by 1971, Bell researchers led by Michael Tompsett were able to capture images with simple linear devices. Several companies, including Fairchild Semiconductor, RCA and Texas Instruments, picked up on the invention, fairchilds effort, led by ex-Bell researcher Gil Amelio, was the first with commercial devices, and by 1974 had a linear 500-element device and a 2-D100 x 100 pixel device. Steven Sasson, an engineer working for Kodak, invented the first digital still camera using a Fairchild 100 x 100 CCD in 1975. The first KH-11 KENNAN reconnaissance satellite equipped with charge-coupled device array technology for imaging was launched in December 1976, under the leadership of Kazuo Iwama, Sony also started a large development effort on CCDs involving a significant investment. Eventually, Sony managed to mass-produce CCDs for their camcorders, before this happened, Iwama died in August 1982, subsequently, a CCD chip was placed on his tombstone to acknowledge his contribution. He was also awarded the 2012 IEEE Edison Medal For pioneering contributions to imaging devices including CCD Imagers, cameras, in a CCD for capturing images, there is a photoactive region, and a transmission region made out of a shift register. An image is projected through a lens onto the capacitor array, once the array has been exposed to the image, a control circuit causes each capacitor to transfer its contents to its neighbor. The last capacitor in the array dumps its charge into a charge amplifier, by repeating this process, the controlling circuit converts the entire contents of the array in the semiconductor to a sequence of voltages
9.
Active pixel sensor
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An active-pixel sensor is an image sensor consisting of an integrated circuit containing an array of pixel sensors, each pixel containing a photodetector and an active amplifier. Such an image sensor is produced using CMOS technology, and has emerged as an alternative to charge-coupled device image sensors. The term active pixel sensor was coined in 1985 by Tsutomu Nakamura who worked on the Charge Modulation Device active pixel sensor at Olympus, the MOS passive-pixel sensor used just a simple switch in the pixel to read out the photodiode integrated charge. Pixels were arrayed in a structure, with an access enable wire shared by pixels in the same row. At the end of each column was an amplifier, passive-pixel sensors suffered from many limitations, such as high noise, slow readout, and lack of scalability. The addition of an amplifier to each pixel addressed these problems, Noble in 1968 and Chamberlain in 1969 created sensor arrays with active MOS readout amplifiers per pixel, in essentially the modern three-transistor configuration. The CCD was invented in October 1969 at Bell Labs, a low-resolution mostly digital N-channel MOSFET imager with intra-pixel amplification, for an optical mouse application, was demonstrated in 1981. Another type of active pixel sensor is the infrared focal plane array designed to operate at cryogenic temperatures in the infrared spectrum. The exact date of origin of these devices is classified, by the late 1980s and early 1990s, the CMOS process was well established as a well controlled stable process and was the baseline process for almost all logic and microprocessors. Between 1993 and 1995, the Jet Propulsion Laboratory developed a number of prototype devices, though primitive, these devices demonstrated good image performance with high readout speed and low power consumption. In 1995, personnel from JPL founded Photobit Corp, many other small image sensor companies also sprang to life shortly thereafter due to the accessibility of the CMOS process and all quickly adopted the active pixel sensor approach. Most recent, the CMOS sensor technology has spread to medium-format photography with Phase One being the first to launch a medium format digital back with a Sony-built CMOS sensor, APS pixels solve the speed and scalability issues of the passive-pixel sensor. They generally consume less power than CCDs, have less image lag, unlike CCDs, APS sensors can combine the image sensor function and image processing functions within the same integrated circuit. APS sensors have found markets in many applications, especially camera phones. They have also used in other fields including digital radiography, military ultra high speed image acquisition, security cameras. Manufacturers include Aptina Imaging, Canon, Samsung, STMicroelectronics, Toshiba, OmniVision Technologies, Sony, cMOS-type APS sensors are typically suited to applications in which packaging, power management, and on-chip processing are important. CMOS type sensors are used, from high-end digital photography down to mobile-phone cameras. A big advantage of a CMOS sensor is that it is less expensive than a CCD sensor
10.
Camera
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Thumb|A2016 Nikon D810 A camera is an optical instrument for recording or capturing images, which may be stored locally, transmitted to another location, or both. The images may be individual still photographs or sequences of images constituting videos or movies, the camera is a remote sensing device as it senses subjects without physical contact. The word camera comes from camera obscura, which means dark chamber and is the Latin name of the device for projecting an image of external reality onto a flat surface. The modern photographic camera evolved from the camera obscura, the functioning of the camera is very similar to the functioning of the human eye. A camera may work with the light of the spectrum or with other portions of the electromagnetic spectrum. A still camera is a device which creates a single image of an object or scene. All cameras use the basic design, light enters an enclosed box through a converging lens/convex lens. A shutter mechanism controls the length of time that light can enter the camera, a display, often a liquid crystal display, permits the user to view scene to be recorded and settings such as ISO speed, exposure, and shutter speed. A movie camera or a video camera operates similarly to a camera, except it records a series of static images in rapid succession. When the images are combined and displayed in order, the illusion of motion is achieved, the forerunner to the photographic camera was the camera obscura. The oldest known record of this principle is a description by Han Chinese philosopher Mozi, Mozi correctly asserted that the camera obscura image is inverted because light travels in straight lines from its source. In the 11th century Arab physicist Ibn al-Haytham s wrote very influential essays about experiments with light through an opening in a darkened room. The use of a lens in the opening of a wall or closed window shutter of a room to project images used as a drawing aid has been traced back to circa 1550. Since the late 17th century portable camera obscura devices in tents, before the development of the photographic camera, it had been known for hundreds of years that some substances, such as silver salts, darkened when exposed to sunlight. The first person to use this chemistry to create images was Thomas Wedgwood, to create images, Wedgwood placed items, such as leaves and insect wings, on ceramic pots coated with silver nitrate, and exposed the set-up to light. These images werent permanent, however, as Wedgwood didnt employ a fixing mechanism and he ultimately failed at his goal of using the process to create fixed images created by a camera obscura. The first permanent photograph of an image was made in 1826 by Joseph Nicéphore Niépce using a sliding wooden box camera made by Charles. Niépce had been experimenting with ways to fix the images of a camera obscura since 1816, the photograph Niépce succeeded in creating shows the view from his window
11.
Camera lens
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A lens might be permanently fixed to a camera, or it might be interchangeable with lenses of different focal lengths, apertures, and other properties. While in principle a simple convex lens will suffice, in practice a compound made up of a number of optical lens elements is required to correct the many optical aberrations that arise. Some aberrations will be present in any lens system and it is the job of the lens designer to balance these and produce a design that is suitable for photographic use and possibly mass production. Typical rectilinear lenses can be thought of as improved pinhole lenses, as shown, a pinhole lens is simply a small aperture that blocks most rays of light, ideally selecting one ray to the object for each point on the image sensor. Here a pixel is the area of the detector exposed to light from a point on the object, making the pinhole smaller improves resolution, but reduces the amount of light captured. At a certain point, shrinking the hole does not improve the resolution because of the diffraction limit, beyond this limit, making the hole smaller makes the image blurrier as well as darker. Practical lenses can be thought of as an answer to the question how can a pinhole lens be modified to more light. A first step is to put a simple convex lens at the pinhole with a length equal to the distance to the film plane. The geometry is almost the same as with a pinhole lens. From the front of the camera, the hole, would be seen. If one were inside the camera, one would see the acting as a projector. The virtual image of the aperture from inside the camera is the exit pupil. Practical photographic lenses include more lens elements, a camera lens may be made from a number of elements, from one, as in the Box Brownies meniscus lens, to over 20 in the more complex zooms. These elements may themselves comprise a group of lenses cemented together, the front element is critical to the performance of the whole assembly. In all modern lenses the surface is coated to reduce abrasion, flare, and surface reflectance, to minimize aberration, the curvature is usually set so that the angle of incidence and the angle of refraction are equal. In a prime lens this is easy, but in a zoom there is always a compromise, the lens usually is focused by adjusting the distance from the lens assembly to the image plane, or by moving elements of the lens assembly. To improve performance, some lenses have a cam system that adjusts the distance between the groups as the lens is focused, manufacturers call this different things, Nikon calls it CRC, Canon calls it a floating system, and Hasselblad and Mamiya call it FLE. Glass is the most common used to construct lens elements, due to its good optical properties
12.
Visible spectrum
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The visible spectrum is the portion of the electromagnetic spectrum that is visible to the human eye. Electromagnetic radiation in this range of wavelengths is called light or simply light. A typical human eye will respond to wavelengths from about 390 to 700 nm, in terms of frequency, this corresponds to a band in the vicinity of 430–770 THz. The spectrum does not, however, contain all the colors that the human eyes, unsaturated colors such as pink, or purple variations such as magenta, are absent, for example, because they can be made only by a mix of multiple wavelengths. Colors containing only one wavelength are called pure colors or spectral colors. Visible wavelengths pass through the window, the region of the electromagnetic spectrum that allows wavelengths to pass largely unattenuated through the Earths atmosphere. An example of this phenomenon is that clean air scatters blue light more than red wavelengths, the optical window is also referred to as the visible window because it overlaps the human visible response spectrum. The near infrared window lies just out of the vision, as well as the Medium Wavelength IR window. In the 13th century, Roger Bacon theorized that rainbows were produced by a process to the passage of light through glass or crystal. In the 17th century, Isaac Newton discovered that prisms could disassemble and reassemble white light and he was the first to use the word spectrum in this sense in print in 1671 in describing his experiments in optics. The result is red light is bent less sharply than violet as it passes through the prism. Newton divided the spectrum into seven named colors, red, orange, yellow, green, blue, indigo, the human eye is relatively insensitive to indigos frequencies, and some people who have otherwise-good vision cannot distinguish indigo from blue and violet. For this reason, some commentators, including Isaac Asimov, have suggested that indigo should not be regarded as a color in its own right. However, the evidence indicates that what Newton meant by indigo, comparing Newtons observation of prismatic colors to a color image of the visible light spectrum shows that indigo corresponds to what is today called blue, whereas blue corresponds to cyan. In the 18th century, Goethe wrote about optical spectra in his Theory of Colours, Goethe used the word spectrum to designate a ghostly optical afterimage, as did Schopenhauer in On Vision and Colors. Goethe argued that the spectrum was a compound phenomenon. Where Newton narrowed the beam of light to isolate the phenomenon, Goethe observed that a wider aperture produces not a spectrum but rather reddish-yellow, the spectrum appears only when these edges are close enough to overlap. Young was the first to measure the wavelengths of different colors of light, the connection between the visible spectrum and color vision was explored by Thomas Young and Hermann von Helmholtz in the early 19th century
13.
Eye
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Eyes are organs of the visual system. They provide organisms vision, the ability to process visual detail, eyes detect light and convert it into electro-chemical impulses in neurons. Eyes with resolving power have come in ten different forms. Image-resolving eyes are present in molluscs, chordates and arthropods, the simplest eyes, such as those in microorganisms, do nothing but detect whether the surroundings are light or dark, which is sufficient for the entrainment of circadian rhythms. Complex eyes can distinguish shapes and colours, the visual fields of many organisms, especially predators, involve large areas of binocular vision to improve depth perception. In other organisms, eyes are located so as to maximise the field of view, such as in rabbits and horses, the first proto-eyes evolved among animals 600 million years ago about the time of the Cambrian explosion. The last common ancestor of animals possessed the biochemical toolkit necessary for vision, in most vertebrates and some molluscs, the eye works by allowing light to enter and project onto a light-sensitive panel of cells, known as the retina, at the rear of the eye. The cone cells and the rod cells in the retina detect, the visual signals are then transmitted to the brain via the optic nerve. The eyes of most cephalopods, fish, amphibians and snakes have fixed lens shapes, and focusing vision is achieved by telescoping the lens—similar to how a camera focuses. Compound eyes are found among the arthropods and are composed of many simple facets which, depending on the details of anatomy, may give either a single pixelated image or multiple images, each sensor has its own lens and photosensitive cell. Some eyes have up to 28,000 such sensors, which are arranged hexagonally, compound eyes are very sensitive to motion. Some arthropods, including many Strepsiptera, have eyes of only a few facets, each with a retina capable of creating an image. With each eye viewing a different thing, an image from all the eyes is produced in the brain, providing very different. Possessing detailed hyperspectral colour vision, the Mantis shrimp has been reported to have the worlds most complex colour vision system, trilobites, which are now extinct, had unique compound eyes. They used clear calcite crystals to form the lenses of their eyes, in this, they differ from most other arthropods, which have soft eyes. The number of lenses in such an eye varied, however, some trilobites had only one, in contrast to compound eyes, simple eyes are those that have a single lens. For example, jumping spiders have a pair of simple eyes with a narrow field of view. Some insect larvae, like caterpillars, have a different type of simple eye which gives a rough image, some of the simplest eyes, called ocelli, can be found in animals like some of the snails, which cannot actually see in the normal sense
14.
John Herschel
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Sir John Frederick William Herschel, 1st Baronet KH FRS was an English polymath, mathematician, astronomer, chemist, inventor, and experimental photographer, who also did valuable botanical work. He was the son of Mary Baldwin and astronomer William Herschel, nephew of astronomer Caroline Herschel, Herschel originated the use of the Julian day system in astronomy. He named seven moons of Saturn and four moons of Uranus, Herschel was born in Slough, Buckinghamshire, the son of Mary Baldwin and William Herschel. He studied shortly at Eton College and St Johns College, Cambridge and it was during his time as an undergraduate that he became friends with Charles Babbage and George Peacock. He left Cambridge in 1816 and started working with his father and he took up astronomy in 1816, building a reflecting telescope with a mirror 18 inches in diameter and with a 20-foot focal length. Between 1821 and 1823 he re-examined, with James South, the stars catalogued by his father. He was one of the founders of the Royal Astronomical Society in 1820, Herschel was made a Knight of the Royal Guelphic Order in 1831. He served as President of the Royal Astronomical Society three times, 1827–29, 1839–41 and 1847–49, a further complementary volume was published posthumously, as the General Catalogue of 10,300 Multiple and Double Stars. His views were published in an article entitled Light in 1828, the voyage to South Africa was made in order to catalogue the stars, nebulae, and other objects of the southern skies. This was to be a completion as well as extension of the survey of the northern heavens undertaken initially by his father William Herschel. He arrived in Cape Town on 15 January 1834 and set up a private 21 ft telescope at Feldhausen at Claremont, amongst his other observations during this time was that of the return of Comet Halley. Herschel collaborated with Thomas Maclear, the Astronomer Royal at the Cape of Good Hope, during this time, he also witnessed the Great Eruption of Eta Carinae. While in southern Africa, he engaged in a variety of scientific pursuits free from a sense of strong obligations to a larger scientific community. It was, he recalled, probably the happiest time in his life. Herschel used a camera lucida to obtain accurate outlines of the specimens, some 112 of the 132 known flower studies were collected and published as Flora Herscheliana in 1996. As their home during their stay in the Cape, the Herschels had selected Feldhausen, here John set up his reflector to begin his survey of the southern skies. — we must not impugn the Scripture Chronology, but we must interpret it in accordance with whatever shall appear on fair enquiry to be the truth for there cannot be two truths. And really there is enough, for the lives of the Patriarchs may as reasonably be extended to 5000 or 50000 years apiece as the days of Creation to as many thousand millions of years
15.
Greek language
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Greek is an independent branch of the Indo-European family of languages, native to Greece and other parts of the Eastern Mediterranean. It has the longest documented history of any living language, spanning 34 centuries of written records and its writing system has been the Greek alphabet for the major part of its history, other systems, such as Linear B and the Cypriot syllabary, were used previously. The alphabet arose from the Phoenician script and was in turn the basis of the Latin, Cyrillic, Armenian, Coptic, Gothic and many other writing systems. Together with the Latin texts and traditions of the Roman world, during antiquity, Greek was a widely spoken lingua franca in the Mediterranean world and many places beyond. It would eventually become the official parlance of the Byzantine Empire, the language is spoken by at least 13.2 million people today in Greece, Cyprus, Italy, Albania, Turkey, and the Greek diaspora. Greek roots are used to coin new words for other languages, Greek. Greek has been spoken in the Balkan peninsula since around the 3rd millennium BC, the earliest written evidence is a Linear B clay tablet found in Messenia that dates to between 1450 and 1350 BC, making Greek the worlds oldest recorded living language. Among the Indo-European languages, its date of earliest written attestation is matched only by the now extinct Anatolian languages, the Greek language is conventionally divided into the following periods, Proto-Greek, the unrecorded but assumed last ancestor of all known varieties of Greek. The unity of Proto-Greek would have ended as Hellenic migrants entered the Greek peninsula sometime in the Neolithic era or the Bronze Age, Mycenaean Greek, the language of the Mycenaean civilisation. It is recorded in the Linear B script on tablets dating from the 15th century BC onwards, Ancient Greek, in its various dialects, the language of the Archaic and Classical periods of the ancient Greek civilisation. It was widely known throughout the Roman Empire, after the Roman conquest of Greece, an unofficial bilingualism of Greek and Latin was established in the city of Rome and Koine Greek became a first or second language in the Roman Empire. The origin of Christianity can also be traced through Koine Greek, Medieval Greek, also known as Byzantine Greek, the continuation of Koine Greek in Byzantine Greece, up to the demise of the Byzantine Empire in the 15th century. Much of the written Greek that was used as the language of the Byzantine Empire was an eclectic middle-ground variety based on the tradition of written Koine. Modern Greek, Stemming from Medieval Greek, Modern Greek usages can be traced in the Byzantine period and it is the language used by the modern Greeks, and, apart from Standard Modern Greek, there are several dialects of it. In the modern era, the Greek language entered a state of diglossia, the historical unity and continuing identity between the various stages of the Greek language is often emphasised. Greek speakers today still tend to regard literary works of ancient Greek as part of their own rather than a foreign language and it is also often stated that the historical changes have been relatively slight compared with some other languages. According to one estimation, Homeric Greek is probably closer to demotic than 12-century Middle English is to modern spoken English, Greek is spoken by about 13 million people, mainly in Greece, Albania and Cyprus, but also worldwide by the large Greek diaspora. Greek is the language of Greece, where it is spoken by almost the entire population
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Photography and the law
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The intellectual property rights on photographs are protected in different jurisdictions by the laws governing copyright and moral rights. In some cases photography may be restricted by civil or criminal law, publishing certain photographs can be restricted by privacy or other laws. Photography of certain subject matter can be restricted in the interests of public morality. Reactions to photography differ between societies, and even there are no official restrictions there may be objections to photographing people or places. Reactions may range from complaints to violence for photography which is not illegal, in the United Kingdom there are no laws forbidding photography of private property from a public place. Photography on private land is not restricted if the landowner has given permission, however, landowners are permitted to impose any conditions they wish upon entry to a property, including forbidding or restricting photography. Persistent or aggressive photography of an individual may come under the legal definition of harassment. This includes photographs taken in a building or the precincts of the court. Taking a photograph in a court can be seen as a serious offence, the prohibition on taking photographs in the precincts is vague. It was designed to prevent the undermining of the dignity of the court, photography of certain subject matter is restricted in the United Kingdom. In particular, the Protection of Children Act 1978 restricts making or possessing pornography of children under 18, there is no law prohibiting photographing children in public spaces. There is a defence of acting with an excuse, however. A PCSO in 2009 cited Section 44 of the Terrorism Act 2000 to prevent a member of the public photographing him, Section 44 actually concerns stop and search powers. However, in January 2010 the stop-and-search powers granted under Section 44 were ruled illegal by the European Court of Human Rights, there is an identical defence of reasonable excuse. This offence covers only a photograph as described in s.2 of the Terrorism Act 2006, as such, it must be of a kind likely to provide practical assistance to a person committing or preparing an act of terrorism. Whether the photograph in question is such is a matter for a jury, the photograph must contain information of such a nature as to raise a reasonable suspicion that it was intended to be used to assist in the preparation or commission of an act of terrorism. It must call for an explanation, whilst photographs are classified as artistic works, the subsistence of copyright does not depend on artistic merit. The owner of the copyright in the photograph is the photographer – the person who creates it, by default
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History of photography
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In the mid-1820s, Nicéphore Niépce succeeded, but several days of exposure in the camera were required and the earliest results were very crude. Niépces associate Louis Daguerre went on to develop the daguerreotype process, the daguerreotype required only minutes of exposure in the camera, and produced clear, finely detailed results. It was commercially introduced in 1839, a generally accepted as the birth year of practical photography. The metal-based daguerreotype process soon had some competition from the paper-based calotype negative, subsequent innovations made photography easier and more versatile. In the mid-20th century, developments made it possible for amateurs to take pictures in color as well as in black-and-white. The commercial introduction of computer-based electronic digital cameras in the 1990s soon revolutionized photography, the coining of the word photography is usually attributed to Sir John Herschel in 1839. It is based on the Greek φῶς, meaning light, and γραφή, meaning drawing, writing, Photography is the result of combining several different technical discoveries. Long before the first photographs were made, Greek mathematicians Aristotle, daniel Barbaro described a diaphragm in 1568. Wilhelm Homberg described how light darkened some chemicals in 1694, the novel Giphantie described what could be interpreted as photography. In 1614, Angelo Sala demonstrated that silver nitrate is blackened by the sun. This discovery of the effect on powdered silver nitrate was not supported and was subsequently disregarded by then-respected scientists who said that his discovery had no practical application. But what he noticed and found to be strange was that part of it remained white and he then observed a cord hanging down and going across in front of the window, which he found out to be the cause. On further examination, he found that the entire mixture inevitably reverted to its white color. Experimenting further, Schulze succeeded in transferring words he pasted on the bottle printed into the substance. ”He put the silver nitrate in an oven and this proved to him, definitively, that heat had not facilitated the transformation, as popularly suspected. Of greater potential usefulness, Scheele found that ammonia dissolved the silver chloride and this discovery, which could have been used to stabilize or fix a camera image captured with silver chloride, was little-noticed at the time and unknown to the earliest photography experimenters. It was not until around the year 1800 that Thomas Wedgwood made the first known attempt to capture the image in a camera obscura by means of a light-sensitive substance and he used paper or white leather treated with silver nitrate. The shadow images eventually darkened all over because o attempts that have made to prevent the uncoloured part of the copy or profile from being acted upon by light have as yet been successful. Wedgwood may have abandoned his experiments due to frail and failing health
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Exposure (photography)
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In photography, exposure is the amount of light per unit area reaching a photographic film or electronic image sensor, as determined by shutter speed, lens aperture and scene luminance. Exposure is measured in lux seconds, and can be computed from exposure value, in photographic jargon, an exposure generally refers to a single shutter cycle. For the same speed, the accumulated photometric exposure should be similar in both cases. A photograph may be described as underexposed when it has a loss of detail, that is. As the adjacent image shows, these terms are technical ones, there are three types of settings, manual, automatic and exposure compensation. Radiant exposure of a surface, denoted He and measured in J/m2, is given by H e = E e t, where Ee is the irradiance of the surface, measured in W/m2, t is the exposure duration, measured in s. Luminous exposure of a surface, denoted Hv and measured in lx⋅s, is given by H v = E v t, many photographic materials are also sensitive to invisible light, which can be a nuisance, or a benefit. The use of units is appropriate to characterize such sensitivity to invisible light. In sensitometric data, such as curves, the log exposure is conventionally expressed as log10. Photographers more familiar with base-2 logarithmic scales can convert using log2 ≈3.32 log10, correct exposure may be defined as an exposure that achieves the effect the photographer intended. A more technical approach recognises that a film has a physically limited useful exposure range. If, for any part of the photograph, the exposure is outside this range. In a very simple model, for example, out-of-range values would be recorded as black or white rather than the precisely graduated shades of colour and this ensures that no significant information is lost during capture. However, it is much easier to discard recorded information during post processing than to try to re-create unrecorded information. In a scene with strong or harsh lighting, the ratio between highlight and shadow luminance values may well be larger than the ratio between the maximum and minimum useful exposure values. A photograph may be described as underexposed when it has a loss of detail, that is. In manual mode, the photographer adjusts the lens aperture and/or shutter speed to achieve the desired exposure, manual exposure calculations may be based on some method of light metering with a working knowledge of exposure values, the APEX system and/or the Zone System. A camera in automatic exposure mode automatically calculates and adjusts exposure settings to match the subjects mid-tone to the mid-tone of the photograph, for most cameras this means using an on-board TTL exposure meter
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Louis Daguerre
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Louis-Jacques-Mandé Daguerre was a French artist and photographer, recognized for his invention of the daguerreotype process of photography. He became known as one of the fathers of photography, though he is most famous for his contributions to photography, he was also an accomplished painter and a developer of the diorama theatre. Louis Daguerre was born in Cormeilles-en-Parisis, Val-dOise, France and he was apprenticed in architecture, theatre design, and panoramic painting to Pierre Prévost, the first French panorama painter. Exceedingly adept at his skill of theatrical illusion, he became a designer for the theatre, and later came to invent the diorama. In 1829, Daguerre partnered with Nicéphore Niépce, an inventor who had produced the worlds first heliograph in 1822, Niépce died suddenly in 1833, but Daguerre continued experimenting, and evolved the process which would subsequently be known as the daguerreotype. After efforts to interest private investors proved fruitless, Daguerre went public with his invention in 1839, under assurances of strict confidentiality, Daguerre explained and demonstrated the process only to the Academys perpetual secretary François Arago, who proved to be an invaluable advocate. Members of the Academy and other individuals were allowed to examine specimens at Daguerres studio. The images were enthusiastically praised as nearly miraculous, and news of the daguerreotype quickly spread, in 1839, he was elected to the National Academy of Design as an Honorary Academician. Daguerre died on 10 July 1851 in Bry-sur-Marne,12 km from Paris, a monument marks his grave there. Daguerres name is one of the 72 names inscribed on the Eiffel tower, in the mid-1820s, prior to his association with Daguerre, Niépce used a coating of bitumen of Judea to make the first permanent camera photographs. The bitumen was hardened where it was exposed to light and the portion was then removed with a solvent. A camera exposure lasting for hours or days was required, Niépce and Daguerre later refined this process, but unacceptably long exposures were still needed. After the death of Niépce in 1833, Daguerre concentrated his attention on the properties of silver salts. The plate was exposed in the camera. Upon seeing the image, the contents of which are unknown, Daguerre said, the latent image on a daguerreotype plate was developed by subjecting it to the vapor given off by mercury heated to 75 °C. The resulting visible image was then fixed by removing the silver iodide with concentrated and heated salt water. Later, a solution of the more effective hypo was used instead, the resultant plate produced an exact reproduction of the scene. The image was laterally reversed—as images in mirrors are—unless a mirror or inverting prism was used during exposure to flip the image, daguerreotypes were usually portraits, the rarer landscape views and other unusual subjects are now much sought-after by collectors and sell for much higher prices than ordinary portraits
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Silver halide
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A silver halide is one of the chemical compounds that can form between the element silver and one of the halogens. In particular, bromine, chlorine, iodine and fluorine may each combine with silver to silver bromide, silver chloride, silver iodide. As a group, they are referred to as the silver halides. Silver halides are light-sensitive chemicals, and are used in photographic film. The gelatin is a part of the emulsion as the protective colloid of appropriate physical and chemical properties. Gelatin may also contain elements which increase the light sensitivity of the emulsion. When a silver halide crystal is exposed to light, a sensitivity speck on the surface of the crystal is turned into a speck of metallic silver. If the speck of silver contains approximately four or more atoms, areas of the emulsion receiving larger amounts of light undergo the greatest development and therefore results in the highest optical density. Silver bromide and silver chloride may be used separately or combined, depending on the sensitivity, silver fluoride is not used in photography. Silver halides are used to make corrective lenses darken when exposed to ultraviolet light. Silver halides, except for silver fluoride, are insoluble in water. Silver nitrate can be used to precipitate halides, this application is useful in analysis of halides. The three main silver halide compounds have distinctive colours that can be used to quickly identify halide ions in a solution, the silver chloride compound forms a white precipitate, silver bromide a creamy coloured precipitate and silver iodide a yellow coloured precipitate. However, close attention is necessary for other compounds in the test solution, some compounds can considerably increase or decrease the solubility of AgX. Examples of compounds that increase the solubility include, cyanide, thiocyanate, thiosulfate, thiourea, amines, ammonia, sulfite, thioether, scientists from Tel Aviv University are experimenting with silver halide optical fibers for transmitting mid-infrared light from carbon dioxide lasers. The fibers allow laser welding of human tissue, as an alternative to traditional sutures
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Silver iodide
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Silver iodide is an inorganic compound with the formula AgI. The compound is a yellow solid, but samples almost always contain impurities of metallic silver that give a gray coloration. The silver contamination arises because AgI is highly photosensitive and this property is exploited in silver-based photography. Silver iodide is used as an antiseptic and in cloud seeding. The structure adopted by silver iodide is temperature dependent, Below 420 K and this phase is encountered in nature as the mineral iodargyrite. Above 420 K, the α-phase becomes more stable and this motif is a body-centered cubic structure which has the silver centers distributed randomly between 6 octahedral,12 tetrahedral and 24 trigonal sites. At this temperature, Ag+ ions can move rapidly through the solid, the transition between the β and α forms represents the melting of the silver sublattice. The entropy of fusion for α-AgI is approximately half that for sodium chloride and this can be rationalized by considering the AgI crystalline lattice to have already partly melted in the transition between α and β polymorphs. A metastable γ-phase also exists below 420 K with the zinc blende structure, silver iodide is prepared by reaction of an iodide solution with a solution of silver ions. The solid is a mixture of the two principal phases, dissolution of the AgI in hydroiodic acid, followed by dilution with water precipitates β-AgI. Alternatively, dissolution of AgI in a solution of concentrated silver nitrate followed by dilution affords α-AgI, if the preparation is not conducted in the absence of sunlight, the solid darkens rapidly, the light causing the reduction of ionic silver to metallic. The photosensitivity varies with sample purity, the crystalline structure of β-AgI is similar to that of ice, allowing it to induce freezing by the process known as heterogeneous nucleation. Approximately 50,000 kg are used for cloud seeding annually, extreme exposure can lead to argyria, characterized by localized discoloration of body tissue
22.
Latent image
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A latent image is an invisible image produced by the exposure to light of a photosensitive material such as photographic film. When photographic film is developed, the area that was exposed darkens, in more physical terms, a latent image is a small cluster of metallic silver atoms formed in or on a silver halide crystal due to reduction of interstitial silver ions by photoelectrons. If intense exposure continues, such photolytic silver clusters grow to visible sizes and this is called printing out the image. On the other hand, the formation of an image by the action of photographic developer is called developing out the image. The size of a cluster in the latent image can be as small as a few silver atoms. However, in order to act as a latent image center. On the other hand, a developed silver grain can have billions of silver atoms, therefore, photographic developer acting on the latent image is a chemical amplifier with a gain factor up to several billion. The development system was the most important technology that increased the sensitivity in the history of photography. The action of the light on the silver halide grains within the emulsion forms sites of metallic silver in the grains, the basic mechanism by which this happens was first proposed by R W Gurney and N F Mott in 1938. The incoming photon liberates an electron, called a photoelectron, from a silver halide crystal, photoelectrons migrate to a shallow electron trap site, where the electrons reduce silver ions to form a metallic silver speck. A positive hole must also be generated but it is largely ignored, subsequent work has slightly modified this picture, so that hole trapping is also considered. Since then, understanding of the mechanism of sensitivity and latent image formation has been greatly improved, one very important way to increase photographic sensitivity is to manipulate the electron traps in each crystal. A pure, defect-free crystal exhibits poor photographic sensitivity, since it lacks a shallow electron trap that facilitates the formation of a latent image, in such a case, many of the photoelectrons will recombine with the silver halide crystal and be wasted. Shallow electron traps are created by sulfur sensitization, introduction of a crystalline defect, the location, kind and number of shallow traps have a huge influence on the efficiency by which the photoelectrons create latent image centers, and consequently, on photographic sensitivity. Another important way to increase photographic sensitivity is to reduce the size of developable latent images. Gold sensitization of Koslowski creates metallic gold specks on the crystal surface, when a latent image is formed around the gold speck, the presence of gold is known to reduce the number of metallic silver atoms necessary to render the crystal developable. Another important concept in increasing photographic sensitivity is to separate photoholes away from photoelectrons and this should reduce the probability of recombination. Reduction sensitization is one implementation of this concept
23.
Daguerreotype
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Daguerreotype process, or daguerreotypy, was the first publicly available photographic process, and for nearly twenty years it was the one most commonly used. During the past few decades, there has been a revival of daguerreotypy among photographers interested in making artistic use of early photographic processes. The darkest areas of the image are simply bare silver, lighter areas have a microscopically fine light-scattering texture, the surface is very delicate, and even the lightest wiping can permanently scuff it. Some tarnish around the edges is normal, the name daguerreotype correctly refers only to one very specific image type and medium, the product of a process that was in wide use only from the early 1840s to the late 1850s. Since the Renaissance era, artists and inventors had searched for a method of capturing visual scenes. Later, with the advent of Modernism, the absence of perspective in art from China, Japan. To copy these images was the first object of Mr. Daguerre met with Niépce, Niépce had invented an early internal combustion engine together with his brother Claude and made improvements to the velocipede, as well as experimenting with lithography and related processes. Their correspondence reveals that Niépce was at first reluctant to any details of his work with photographic images. To guard against letting any secrets out before the invention had been improved,15, for example, signified the tanning action of the sun on human skin,34 - a camera obscura,74 - sulphuric acid. Niépce undertook to release details of the process he had invented - the asphalt process or heliography, Daguerre was sworn to secrecy under penalty of damages, and undertook to design a camera and improve the process. The improved process was named the physautotype. Niépces early experiments had derived from his interest in lithography, the asphalt process, or heliography required exposures that were so long that Arago said it was not fit for use. Nevertheless, without Niépces experiments, it is unlikely that Daguerre would have been able to build on them to adapt, after Niépces death in 1833, his son, Isidore, inherited rights in the contract and a new version was drawn up between Daguerre and Isidore. It would bear Daguerres name alone and this was the daguerreotype process that used iodized silvered plates and was developed with mercury fumes. To exploit the invention four hundred shares would be on offer for a thousand francs each, or, the rights of the process could be bought for twenty thousand francs. Everyone says it is superb, but it will cost us the thousand francs before we learn it and be able to judge if it could remain secret. M. de Mandelot himself knows several persons who could subscribe but will not do so because they think it would be revealed by itself, and now I have proof that many think in this way. I entirely agree with the idea of M. Arago, that is get the government to purchase this discovery, nevertheless, he benefited from the state pension awarded to him together with Daguerre
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Ambrotype
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The ambrotype or amphitype, also known as a collodion positive in the UK, is a positive photograph on glass made by a variant of the wet plate collodion process. Like a print on paper, it is viewed by reflected light, like the daguerreotype, which it replaced, and like the prints produced by a Polaroid camera, each is a unique original that could only be duplicated by using a camera to copy it. The ambrotype was introduced in the 1850s, during the 1860s it was superseded by the tintype, a similar photograph on thin black-lacquered iron, hard to distinguish from an ambrotype if under glass. One side of a glass plate was coated with a thin layer of iodized collodion. The plate was exposed in the camera while still wet, exposure times varied from five to sixty seconds or more depending on the brightness of the lighting and the speed of the camera lens. The plate was developed and fixed. The resulting negative, when viewed by reflected light against a background, appears to be a positive image, the clear areas look black. This effect was integrated by backing the plate with black velvet, by taking the picture on a made of dark reddish-colored glass. Either the emulsion side or the side could be coated, if the bare side was blackened. In either case, another plate of glass was put over the fragile emulsion side to protect it, in some instances the protective glass was cemented directly to the emulsion, generally with a balsam resin. This protected the well but tended to darken it. Ambrotypes were sometimes hand-tinted, untinted ambrotypes are monochrome, gray or tan in their lightest areas, the ambrotype was based on the wet plate collodion process invented by Frederick Scott Archer. Ambrotypes were deliberately underexposed negatives made by that process and optimized for viewing as positives instead, in the US, ambrotypes first came into use in the early 1850s. In 1854, James Ambrose Cutting of Boston took out several patents relating to the process and he may be responsible for coining the term ambrotype. An ambrotype, however, appeared dull and drab when compared with the brilliance of a well-made, by the late 1850s, the ambrotype was overtaking the daguerreotype in popularity. youtube. com/watch. v=Z1BtdiA1fDs
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Tintype
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Tintypes enjoyed their widest use during the 1860s and 1870s, but lesser use of the medium persisted into the early 20th century and it has been revived as a novelty in the 21st. Because the lacquered iron support was resilient and did not need drying, the tintype photograph saw more uses and captured a wider variety of settings and subjects than any other photographic type. It was introduced while the daguerreotype was still popular, though its primary competition would have been the ambrotype, the tintype saw the Civil War come and go, documenting the individual soldier and horrific battle scenes. It captured scenes from the Wild West, as it was easy to produce by itinerant photographers working out of covered wagons. It began losing artistic and commercial ground to higher quality albumen prints on paper in the mid-1860s, yet survived for well over another 40 years, the tintypes immediate predecessor, the ambrotype, was done by the same process of using a sheet of glass as the support. The glass was either of a color or provided with a black backing so that, as with a tintype. Tintypes were sturdy and did not require mounting in a hard case like ambrotypes and daguerreotypes. There are two historic tintype processes, wet and dry, in the wet process, a collodion emulsion containing suspended silver halide crystals had to be formed on the plate just before it was exposed in the camera while still wet. Chemical treatment then reduced the crystals to microscopic particles of silver in proportion to the intensity and duration of their exposure to light. The later and more convenient dry process was similar but used a gelatin emulsion which could be applied to the plate long before use, in both processes, a very underexposed negative image was produced in the emulsion. Its densest areas, corresponding to the lightest parts of the subject, the image as a whole therefore appeared to be a dull-toned positive. This ability to employ underexposed images allowed shorter exposure times to be used, to obtain as light-toned an image as possible, potassium cyanide, a very dangerous and powerful deadly poison, was normally employed as the photographic fixer. It was perhaps the most acutely hazardous of all the highly toxic chemicals originally used in this. One unusual piece of equipment was a twelve-lensed camera that could make a dozen 3⁄4-by-1-inch gem portraits with one exposure. Portrait sizes ranged from gem-size to 11 in ×14 in, from about 1865 to 1910, the most popular size, called Bon-ton, ranged from 2 3⁄8 in ×3 1⁄2 in to 4 in ×5 3⁄4 in. Each tintype is usually a camera original, so the image is usually a mirror image, sometimes the camera was fitted with a mirror or right-angle prism so that the end result would be right-reading. The process was first described by Adolphe-Alexandre Martin in France in 1853, in 1856 it was patented by Hamilton Smith in the United States and by William Kloen in the United Kingdom. It was first called melainotype, then ferrotype by a manufacturer of the iron plates used
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Collodion process
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The collodion process is an early photographic process. Collodion is normally used in its wet form, but can also be used in humid or dry form, the latter made the dry form unsuitable for the usual portraiture work of most professional photographers of the 19th century. The use of the dry form was mostly confined to landscape photography. The collodion process is said to have invented in 1851, almost simultaneously, by Frederick Scott Archer. During the subsequent decades, many photographers and experimenters refined or varied the process, by the end of the 1850s it had almost entirely replaced the first practical photographic process, the daguerreotype. During the 1880s the collodion process, was replaced by gelatin dry plates—glass plates with a photographic emulsion of silver halides suspended in gelatin. The dry gelatin emulsion was not only convenient, but it could also be made much more sensitive. The wet plate collodion process has undergone a revival as a historical technique over the past few decades, there are several practising ambrotypists and tintypists who regularly set up and make images at Civil War re-enactments. Fine art photographers use the process and its handcrafted individuality for gallery showings, there are several makers of reproduction equipment. The process is taught in workshops around the world and several workbooks, many artists work with collodion around the globe, including traveling photographer Craig Murphy, Kurt Grüng, Sally Mann, and Ben Cauchi. The collodion process produced an image on a transparent support. The collodion process, thus combined desirable qualities of the calotype process, collodion printing was typically done on albumen paper. The collodion process had other advantages, especially in comparison with the daguerreotype and it was a relatively inexpensive process. The polishing equipment and fuming equipment needed for the daguerreotype could be dispensed with entirely, the support for the images was glass, which was far less expensive than silver-plated copper, and was more durable than paper negatives. It was also fast for the time, requiring only seconds for exposure, the wet collodion process had a major disadvantage. The entire process, from coating to developing, had to be done before the plate dried and this gave the photographer no more than 10 minutes to complete everything. This made it inconvenient for use, as it required a portable darkroom. The plate dripped silver nitrate solution, causing stains and troublesome build-ups in the camera, the silver nitrate bath was also a source of problems
27.
Albumen print
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During the mid-19th century, the carte de visite became one of the more popular uses of the albumen method. In the 19th century, E. & H. T. Anthony & Company were the largest makers and distributors of the Albumen photographic prints, a piece of paper, usually 100% cotton, is coated with an emulsion of egg white and salt, then dried. The albumen seals the paper and creates a slightly glossy surface for the sensitizer to rest on, the paper is then dipped in a solution of silver nitrate and water which renders the surface sensitive to UV light. The paper is then dried in the absence of UV light, the dried, prepared paper is placed in a frame in direct contact under a negative. The negative is traditionally a glass negative with collodion emulsion, but this step can be performed with a silver halide negative. The paper with negative is then exposed to light until the image achieves the level of darkness. Though direct sunlight was used long ago, a UV exposure unit is often used contemporarily because it is more predictable, a bath of sodium thiosulfate fixes the print’s exposure, preventing further darkening. Optional gold or selenium toning improves the photograph’s tone and stabilizes against fading, depending on the toner, toning may be performed before or after fixing the print. Because the image emerges as a result of exposure to light, without the aid of a developing solution. The table salt in the emulsion forms silver chloride when in contact with silver nitrate. Silver chloride is unstable when exposed to light, which makes it decompose into silver, the silver ion is reduced to silver by addition of an electron during the development/printing process, and the remaining silver chloride is washed out during fixing. The black parts of the image are formed by metallic silver, photography, the importance of its applications in preserving pictorial records. Containing a practical description of the Talbotype process, george Eastman House Photographic Process 3. Albumen printing, Creating and processing albumen paper, archived from the original on 2009-01-07
28.
Black and white
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Black and white, often abbreviated B/W or B&W, and hyphenated black-and-white when used as an adjective, is any of several monochrome forms in visual arts. Black-and-white images are not usually starkly contrasted black and white and they combine black and white in a continuum producing a range of shades of gray. Even when most studios had the capability to make color films they were not heavily utilized as using the Technicolor process was expensive, for the years 1940–1966, a separate Academy Award for Best Art Direction was given for black-and-white movies along with one for color. Television, Television program was first transmitted in black-and-white, scottish inventor John Logie Baird demonstrated the worlds first color television transmission on July 3,1928 using a mechanical process. Some color broadcasts in the US began in the 1950s, with color becoming common in industrialized nations during the late 1960s. In the United States, the Federal Communications Commission settled on a color NTSC standard in 1953, color television became more widespread in the U. S. between 1963 and 1967, when the CBS and ABC networks joined NBC in broadcasting full color schedules. Canada began airing color television in 1966 while the United Kingdom began to use a different color system from July 1967 known as PAL. The Republic Of Ireland followed in 1970, in China, black and white television sets were the norm until as late as the 1990s, color TVs not outselling them until about 1989. While seldom used now, many consumer camcorders have the ability to record in black-and-white. Photography, Photographs were either black-and-white or shades of sepia, color photography was originally rare and expensive and again often containing inaccurate hues. Color photography became more common from the mid-20th century, Today, black-and-white is a niche market for photographers who use the medium for artistic purposes. This can take the form of film or digital conversion to grayscale. For amateur use certain companies such as Kodak manufactured black-and-white disposable cameras until 2009, also, certain films are produced today which give black-and-white images using the ubiquitous C41 color process. Printing press, Most American newspapers were black-and-white until the early 1980s, The New York Times, some claim that USA Today was the major impetus for the change to color. In the UK, color was only introduced from the mid-1980s. Even today, many newspapers restrict color photographs to the front, similarly, daily comic strips in newspapers were traditionally black-and-white with color reserved for Sunday strips. Sometimes color is reserved for the cover, magazines such as Jet magazine were either all or mostly black-and-white until the end of the 2000s when it became all-color. Manga are typically published in black-and-white although now it is part of its image, many school yearbooks are still entirely or mostly in black-and-white
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Anthotype
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An anthotype is an image created using photosensitive material from plants. This process was invented by Sir John Herschel in 1842. An emulsion is made from crushed flower petals or any other light-sensitive plant, a coated sheet of paper is then dried. Place some material, for example leaves or a transparent photo positive on the paper, the color remains or fades in the shadowed parts. The paper remains sensitive against such rays, the photo-sensitive properties of plants and vegetables have been known to scholars for centuries. Among many early observations the experiments of Henri August Vogel in Paris are of particular interest, cotton and paper colored with these tinctures exhibited the same differences. Later that century Herschel attempted to invent a process, he tried several flower and plant emulsions. His research resulted in the anthotype process, the process continued to be listed in photographic literature of the time but was likely little used. Over time the process has earned a reputation for being simply too impractical. Image permanence have been brought into question to this day but this seems to be mostly related to choice of flower or plant matter. For instance, yellows tending towards orange are destroyed with more energy by the rays, blues by the red, orange and yellow rays, purples and pinks by yellow. Henry H. Snelling writes based on his research, Viola odorata--or sweet scented violet, yields to alcohol a rich blue color, senecio Splendens--or double purple groundsel, yields a beautiful color to paper. The History and Practice of the Art of Photography, on Gutenberg The anthotype process http, //www. alternativephotography. com/wp/processes/anthotypes/anthotypes-making-print-using-plants
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Louis Arthur Ducos du Hauron
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Louis Arthur Ducos du Hauron was a French pioneer of color photography. He was born in Langon, Gironde and died in Agen, in 1868 he patented his ideas and in 1869 he published them in Les couleurs en photographie, solution du problème. The discovery of dye sensitization by Hermann Wilhelm Vogel in 1873 greatly facilitated the initial analysis on which all of Ducos de Haurons methods depended. The most widely reproduced of his color photographs is the View of Agen. In 1891, he introduced the anaglyph stereoscopic print, the red, colour Photography, The First Hundred Years, 1840-1940
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Lippmann plate
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A Lippmann plate is a clear glass plate, coated with an almost transparent emulsion of extremely fine grains, typically 0.01 to 0.04 micrometres in diameter. Consequently, Lippmann plates have a high resolving power exceeding 400 lines/mm. The standing waves cause exposure of the emulsion in diffraction patterns, the result is an image having very similar colours as the original using a black & white photographic process. For this method Lippmann won the Nobel Prize in Physics in 1908, the colour image can only be viewed in the reflection of a diffuse light source from the plate, making the field of view limited, and it cannot be copied. The technique was very insensitive with the emulsions of the time, another reason Lippmanns process of colour photography did not succeed can be found in the invention of the autochrome plates by the brothers A. and L. Lumière. Lippmann photographic techniques are being developed to produce images which can easily be viewed, kodak Spectroscopic Plate Type 649-F is specified with a resolving power of 2000 lines/mm. Millington, Andrew G. Mayes, Christopher R
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Kodachrome
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Kodachrome is a brand name for a non-substantive, color reversal film introduced by Eastman Kodak in 1935. It was one of the first successful color materials and was used for both cinematography and still photography, because of its complex processing requirements, the film was sold process-paid in the United States until 1954 when a legal ruling prohibited this. For many years it was used for color photography, especially for images intended for publication in print media. After announcing the return of Ektachrome at the beginning of 2017, Kodachrome was the first color film that used a subtractive color method to be successfully mass-marketed. Previous materials, such as Autochrome and Dufaycolor, had used the additive screenplate methods, until its discontinuation, Kodachrome was the oldest surviving brand of color film. Kodachrome is appreciated in the archival and professional market for its dark-storage longevity, because of these qualities, it was used by professional photographers such as Steve McCurry, Peter Guttman and Alex Webb. McCurry used Kodachrome for his 1984 portrait of Sharbat Gula, the Afghan Girl and it was used by Walton Sound and Film Services in the UK in 1953 for the official 16 mm film of the coronation of Elizabeth II of the United Kingdom. Copies of the film for sale to the public were also produced using Kodachrome and these had several disadvantages because they used a réseau filter made from discrete color elements that were visible upon enlargement. The finished transparencies absorbed between 70% and 80% of light projection, requiring very bright projection lamps, especially for large projections. Using the subtractive method, these disadvantages could be avoided, the first Kodak product called Kodachrome was invented by John Capstaff in 1913. His Kodachrome was a process that used only two colors, blue-green and red-orange. It required two glass plate negatives, one using a panchromatic emulsion and a red filter, the other made using an emulsion insensitive to red light. The two plates could be exposed as a bipack, which eliminated the need for multiple exposures or a color camera. After development, the images were bleached out with chemistry that hardened the bleached portions of the gelatin. Using dyes which were absorbed only by the gelatin, the negative that recorded the blue and green light was dyed red-orange. The result was a pair of positive dye images, the plates were then assembled emulsion to emulsion, producing a transparency that was capable of surprisingly good color rendition of skin tones in portraits. Capstaffs Kodachrome was made available in 1915. It was also adapted for use as a 35 mm motion picture film process, today, this first version of Kodachrome is nearly forgotten, completely overshadowed by the next Kodak product bearing the name Kodachrome
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Agfacolor
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Agfacolor was the name of a series of color film products made by Agfa of Germany. The first Agfacolor, introduced in 1932, was a version of their Agfa-Farbenplatte. In late 1936 Agfa introduced Agfacolor Neu, a color film of the general type still in use today. The new Agfacolor was originally a film used for making slides, home movies. By 1939 it had also adapted into a negative film. After World War II, the Agfacolor brand was applied to varieties of color negative film for still photography. The reversal film was marketed as Agfachrome. Agfacolor Neu, called simply Agfacolor after its predecessor had been retired, was the German response to Technicolor, like Kodachrome, introduced by Eastman Kodak in 1935, the new Agfacolor film was an integral tripack with three differently color-sensitized emulsion layers. The Third Reichs Minister of Propaganda Joseph Goebbels was in a hurry and he admired Hollywood movies and examined them carefully in regular private screenings. The use of Agfacolor was reinforced by the top of the Nazi film industry, Reichsminister Joseph Goebbels, Agfacolor was then used throughout the entire film shoot of Women Are Better Diplomats. Throughout the shoot, the film yielded mixed results as it was very sensitive to different color temperatures caused by solar altitude at different times of day. Thus, outdoor shots were difficult to handle, A lawn in front of a castle appeared completely yellow, later brown, meanwhile the production costs had risen from 1.5 to 2.5 million Reichsmarks. More than two years after its date, Women Are Better Diplomats opened in October 1941. Despite its rather weak color quality, the proved to be a major hit. After the processs growing pains had been throughout the production of Women are better diplomats. The technology was improved at a rapid pace, veit Harlan, perhaps the most prominent official film director of the Third Reich, was allowed to shoot his next picture in Agfacolor. The Golden City premièred at the Venice Film Festival in September 1942 and was awarded for its technical quality. Shot by cameraman Werner Krien, who had done black-and-white pictures before, and assisted by special effects specialist Konstantin Irmen-Tschet, made for UFAs 25th Anniversary, Münchhausen was the third German feature film––out of over a dozen––to be produced using Agfacolor film between 1939 and 1945
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Slide projector
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A slide projector is an opto-mechanical device for showing photographic slides. Slide projectors were widely used in educational and other institutional settings. This glass transmits visible wavelengths but absorbs infrared, light passes through the transparent slide and lens, and the resulting image is enlarged and projected onto a perpendicular flat screen so the audience can view its reflection. Alternatively, the image may be projected onto a translucent rear projection screen, often used for continuous automatic display for close viewing and this form of projection also avoids the audience interrupting the light stream by casting their shadows on the projection or by bumping into the projector. Slide projectors get smarter all the time
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Technicolor
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Technicolor is the name applied to a series of color motion picture processes, the first version dating from 1916, and followed by improved versions over several decades. It was the major color process, after Britains Kinemacolor. As the technology matured it was used for less spectacular dramas. Occasionally, even a film noir—such as Leave Her to Heaven or Niagara —was filmed in Technicolor, Technicolor is the trademark for a series of color motion picture processes pioneered by Technicolor Motion Picture Corporation, now a division of the French company Technicolor SA. The Technicolor Motion Picture Corporation was founded in Boston in 1914 by Herbert Kalmus, Daniel Frost Comstock, the Tech in the companys name was inspired by the Massachusetts Institute of Technology, where both Kalmus and Comstock received their undergraduate degrees and were later instructors. Technicolor, Inc. was chartered in Delaware in 1921, most of Technicolors early patents were taken out by Comstock and Wescott, while Kalmus served primarily as the companys president and chief executive officer. The term Technicolor historically has been used to describe at least five concepts, Technicolor, Technicolor process or format, several custom image origination systems used in film production, culminating in the three-strip process in 1932. Technicolor IB printing, a process for making color motion picture prints that allows the use of dyes which are more stable, originally used for printing from color separation negatives photographed on black-and-white film in a special Technicolor camera. This meaning of the name applies to nearly all Wikipedia articles about films made from 1954 onward in which Technicolor is named in the credits, Technicolor originally existed in a two-color system. Because two frames were being exposed at the time, the film had to be photographed and projected at twice the normal speed. Exhibition required a special projector with two apertures, two lenses, and a prism that aligned the two images on the screen. The results were first demonstrated to members of the American Institute of Mining Engineers in New York on February 21,1917, the near-constant need for a technician to adjust the projection alignment doomed this additive color process. Only a few frames of The Gulf Between, showing star Grace Darmond, are known to exist today, convinced that there was no future in additive color processes, Comstock, Wescott, and Kalmus focused their attention on subtractive color processes. This culminated in what would eventually be known as Process 2, the difference was that the two-component negative was now used to produce a subtractive color print. Because the colors were present in the print, no special projection equipment was required. The frames exposed behind the filter were printed on one strip of black-and-white film. After development, each print was toned to a color nearly complementary to that of the filter, orange-red for the green-filtered images, the two prints, made on film stock half the thickness of regular film, were then cemented together back to back to create a projection print. The Toll of the Sea, which debuted on November 26,1922, the second all-color feature in Process 2 Technicolor, Wanderer of the Wasteland, was released in 1924
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Very Large Telescope
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The Very Large Telescope is a telescope facility operated by the European Southern Observatory on Cerro Paranal in the Atacama Desert of northern Chile. The VLT consists of four telescopes, each with a primary mirror 8.2 m across. The four separate optical telescopes are known as Antu, Kueyen, Melipal and Yepun, the telescopes form an array which is complemented by four movable Auxiliary Telescopes of 1.8 m aperture. The VLT operates at visible and infrared wavelengths.001 arc-second and this is equivalent to roughly 2 meters resolution at the distance of the Moon. In single telescope mode of operation angular resolution is about 0.05 arc-second, the VLT is the most productive ground-based facility for astronomy, with only the Hubble Space Telescope generating more scientific papers among facilities operating at visible wavelengths. The VLT consists of an arrangement of four large telescopes with optical elements that can combine them into an astronomical interferometer, the interferometer also includes a set of four 1.8 meter diameter movable telescopes dedicated to interferometric observations. The first of the UTs started operating in May 1998 and was offered to the community on 1 April 1999. The other telescopes followed suit in 1999 and 2000, thus making the VLT fully operational, four 1. 8-metre Auxiliary Telescopes have been added to the VLTI to make it available when the UTs are being used for other projects. These ATs were installed between 2004 and 2007, today, all four Unit Telescopes and all four Auxiliary Telescopes are operational. The VLTs 8. 2-meter telescopes were designed to operate in three modes, as a set of four independent telescopes. as a single large coherent interferometric instrument. This mode is used, only for observations of relatively bright sources with small angular extent. As a single large incoherent instrument, for extra light-gathering capacity, the instrumentation required to bring the light to a combined incoherent focus was not built. Recently, new proposals have been put forward for making this observing mode available. Multiple telescopes are sometimes independently pointed at the object, either to increase the total light-gathering power. In particular, the VLT has several adaptive optics systems, which correct for the effects of atmospheric turbulence, providing images almost as sharp as if the telescope were in space. In the near-infrared, the adaptive optics images of the VLT are up to three times sharper than those of the Hubble Space Telescope, and the resolution is many times better than Hubble. The VLTs are noted for their level of observing efficiency. The 8.2 m-diameter telescopes are housed in compact, thermally controlled buildings, the principal role of the main VLT telescopes is to operate as four independent telescopes
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Photographic paper
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Photographic paper is a paper coated with a light-sensitive chemical formula, used for making photographic prints. The light-sensitive layer of the paper is called the emulsion, the most common chemistry was based on silver salts but other alternatives have also been used. The initial light exposure is carefully controlled to produce a gray scale image on the paper with appropriate contrast and gradation. Photographic paper may also be exposed to light using digital printers such as the LightJet, with a camera, by scanning a modulated light source over the paper, despite the introduction of digital photography, photographic papers are still sold commercially. Photographic papers are manufactured in standard sizes, paper weights. A range of emulsions are also available that differ in their sensitivity, colour response. Colour papers are available for making colour images. The effect of light in darkening a prepared paper was discovered by Thomas Wedgwood in 1802, photographic papers have been used since the beginning of all negative–positive photographic processes as developed and popularized by William Fox Talbot. After the early days of photography, papers have been manufactured on a scale with improved consistency. Photographic papers fall into one of three sub-categories, Papers used for negative-positive processes and this includes all current black-and-white papers and chromogenic colour papers. Papers used for positive-positive processes in which the film is the same as the final image, Papers used for positive-positive film-to-paper processes where a positive image is enlarged and copied onto a photographic paper, for example the Ilfochrome process. In Chromogenic colour papers, the layers are sensitive to red, green and blue light, respectively producing cyan, magenta. Modern black-and-white papers are coated on a range of bases, baryta-coated paper. In the past, linen has been used as a base material, fiber-based photographic papers consist of a paper base coated with baryta. Tints are sometimes added to the baryta to add colour to the final print. Most fiber-based papers include a clear hardened gelatin layer above the emulsion which protects it from physical damage, Papers without a supercoating are suitable for use with the bromoil process. Fiber-based papers are chosen as a medium for high-quality prints for exhibition, display. These papers require careful processing and handling, especially when wet, however, they are easier to tone, hand-colour and retouch than resin-coated equivalents
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Reversal film
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In photography, reversal film is a type of photographic film that produces a positive image on a transparent base. The film is processed to produce transparencies or diapositives instead of negatives, Reversal film is produced in various sizes, from 35 mm roll film to 8×10 inch sheet film. A slide is a specially mounted individual transparency intended for projection onto a screen using a slide projector and this allows the photograph to be viewed by a large audience at once. The most common form is the 35 mm slide, with the image framed in a 2×2 inch cardboard or plastic mount. Reversal film is used as motion picture film, mostly in the 16 mm, Super 8 and 8 mm cine formats. This avoids the expense of using film, which requires additional film. The earliest practical and commercially successful color photography reversal process was the Lumière Autochrome and this was an additive method, using a panchromatic emulsion coated on a thin glass plate previously coated with a layer of dyed potato starch grains. Autochrome plates were discontinued in the 1930s after the introduction of Lumière Filmcolor in sheet film, also using the additive principle and reversal processing were the Agfa color screen plates and films and Dufaycolor film, all of which were discontinued by 1961. Leopold Godowsky, Jr. and Leopold Mannes, working with the Eastman Kodak Company, developed Kodachrome, Kodachrome was introduced in 1935 as 16mm motion picture film, and in 1936 as 35mm film for still cameras. The Kodachrome films contained no color dye couplers, these were added during processing, in late 1936, Agfacolor Neu was launched, Agfa having overcome earlier difficulties with color sensitivity problems. This film had the dye couplers incorporated into the emulsion, making processing simpler than for Kodachrome, amateurs who owned projection equipment used reversal films extensively because the cost of projection equipment and slide film was offset by not having to pay for prints. Eventually, print quality improved and prices decreased, and, by the 1970s, color negative film, digital media gradually replaced transparency film. All color reversal film sold today is developed with the E-6 process, the non-substantive Kodachrome films, the last of which was discontinued in 2009, were processed with the K-14 process. Polaroid produced an instant slide film called Polachrome and it was packaged in cassettes like normal 35mm film. A separate processing unit was used to develop it after exposure, black-and-white transparencies can be made directly with some modern black-and-white films, which normally yield negatives. The negative image is developed but not fixed, the remaining silver halide salts are re-exposed to light, developed and fixed, and the film is washed and dried. Black-and-white transparencies were once popular for presentation of materials using 3 1⁄4 by 4 glass-mounted slides. Such positive black-and-white projection is now rarely done, except in motion pictures, even where black-and-white positives are currently used, the process to create them typically uses an internegative with standard processing instead of a chemical reversal process
Media related to Photographs at Wikimedia Commons
The dictionary definition of photograph at Wiktionary
