SUMMARY / RELATED TOPICS

Flash (photography)

A flash is a device used in photography producing a flash of artificial light at a color temperature of about 5500 K to help illuminate a scene. A major purpose of a flash is to illuminate a dark scene. Other uses are capturing moving objects or changing the quality of light. Flash refers either to the flash of light itself or to the electronic flash unit discharging the light. Most current flash units are electronic, having evolved from single-use flashbulbs and flammable powders. Modern cameras activate flash units automatically. Flash units are built directly into a camera; some cameras allow separate flash units to be mounted via a standardized "accessory mount" bracket. In professional studio equipment, flashes may be large, standalone units, or studio strobes, powered by special battery packs or connected to mains power, they are either synchronized with the camera using a flash synchronization cable or radio signal, or are light-triggered, meaning that only one flash unit needs to be synchronized with the camera, in turn triggers the other units, called slaves.

Studies of magnesium by Robert Bunsen and Henry Enfield Roscoe in 1859 showed that burning this metal produced a light with similar qualities to daylight. The potential application to photography inspired Edward Sonstadt to investigate methods of manufacturing magnesium so that it would burn reliably for this use, he applied for patents in 1862 and by 1864 had started the Manchester Magnesium Company with Edward Mellor. With the help of engineer William Mather, a director of the company, they produced flat magnesium ribbon, said to burn more and so giving better illumination than round wire, it had the benefit of being a simpler and cheaper process than making round wire. Mather was credited with the invention of a holder for the ribbon, which formed a lamp to burn it in. A variety of magnesium ribbon holders were produced by other manufacturers, such as the Pistol Flashmeter, which incorporated an inscribed ruler that allowed the photographer to use the correct length of ribbon for the exposure they needed.

The packaging implies that the magnesium ribbon was not broken off before being ignited. An alternative to ribbon flash powder, a mixture of magnesium powder and potassium chlorate, was introduced by its German inventors Adolf Miethe and Johannes Gaedicke in 1887. A measured amount was put into a pan or trough and ignited by hand, producing a brief brilliant flash of light, along with the smoke and noise that might be expected from such an explosive event; this could be a life-threatening activity if the flash powder was damp. An electrically triggered flash lamp was invented by Joshua Lionel Cowen in 1899, his patent describes a device for igniting photographers’ flash powder by using dry cell batteries to heat a wire fuse. Variations and alternatives were touted from time to time and a few found a measure of success for amateur use. In 1905, one French photographer was using intense non-explosive flashes produced by a special mechanized carbon arc lamp to photograph subjects in his studio, but more portable and less expensive devices prevailed.

On through the 1920s, flash photography meant a professional photographer sprinkling powder into the trough of a T-shaped flash lamp, holding it aloft triggering a brief and harmless bit of pyrotechnics. The use of flash powder in an open lamp was replaced by flashbulbs. Manufactured flashbulbs were first produced commercially in Germany in 1929; such a bulb could only be used once, was too hot to handle after use, but the confinement of what would otherwise have amounted to a small explosion was an important advance. A innovation was the coating of flashbulbs with a plastic film to maintain bulb integrity in the event of the glass shattering during the flash. A blue plastic film was introduced as an option to match the spectral quality of the flash to daylight-balanced colour film. Subsequently, the magnesium was replaced by zirconium. Flashbulbs burned for longer than electronic flashes. Slower shutter speeds were used on cameras to ensure proper synchronization. Cameras with flash sync triggered the flashbulb a fraction of a second before opening the shutter, allowing faster shutter speeds.

A flashbulb used during the 1960s was the Press 25, the 25-millimetre flashbulb used by newspapermen in period movies attached to a press camera or a twin-lens reflex camera. Its peak light output was around a million lumens. Other flashbulbs in common use were the M-series, M-2, M-3 etc. which had a small metal bayonet base fused to the glass bulb. The largest flashbulb produced was the GE Mazda No. 75, being over eight inches long with a girth of 14 inches developed for nighttime aerial photography during World War II. The all-glass PF1 bulb was introduced in 1954. Eliminating both the metal base, the multiple manufacturing steps needed to attach it to the glass bulb, cut the cost compared to the larger M series bulbs; the design required a fibre ring around the base to hold the contact wires against the side of the glass base. An adapter was available allowing the bulb to fit into flash guns that accepted the bayonet capped bulbs; the PF1 had a faster ignition time, so it could be used with X synch below 1/30 of a second—while most bulbs require a shutter speed of 1/

Chhabila Netam

Chhabila Arvind Netam is an Indian National Congress politician and member of the 11th Lok Sabha from the Kanker reserved constituency. Chhabila was born on 22 May 1948 in Bhaismundi village of Bastar district and did her matriculation from a local government school. During the 1996 Indian general election, the Indian National Congress party denied a ticket to Arvind Netam because his name surfaced in the Hawala scandal and instead made his wife Chhabila its official candidate, she polled 219,191 votes and defeated Sohan Potai of Bharatiya Janata Party to become the Member of Parliament from Kanker seat reserved for scheduled tribes. However the house was dissolved well within one and a half years and Netam did not contest the election held in 1998, she lost to Potai by a difference of 88,191 votes. Chhabila married Netam in May 1969 and together they have four children. One of their daughters, Preeti Netam contested the 2008 Chhattisgarh Legislative Assembly election

Arrondissement of Castres

The arrondissement of Castres is an arrondissement of France in the Tarn department in the Occitanie region. Its INSEE code is 812 and its capital city is Castres, it has 151 communes. Its population is 195,298, its area is 3,026.2 km2. It is the southernmost arrondissement of the department; the arrondissement of Castres is bordered to the north by the arrondissement of Albi, to the northeast by the Aveyron department, to the east by the Hérault department, to the south by the Aude department and to the west by the Haute-Garonne department. The communes of the arrondissement of Castres, their INSEE codes, are: The arrondissement of Castres was created in 1800; as a result of the reorganisation of the cantons of France which came into effect in 2015, the borders of the cantons are no longer related to the borders of the arrondissements. The cantons of the arrondissement of Castres were, as of January 2015