In painting, a pentimento is "the presence or emergence of earlier images, forms, or strokes that have been changed and painted over". Sometimes the English form "pentiment" is used, especially in older sources.
The Arnolfini Portrait by Jan van Eyck (1434). Among other changes made, the husband's face was higher by about the height of his eye, the wife's was higher, and her eyes looked more to the front. Each of the husband's feet was underdrawn in one position, painted in another, and then overpainted in a third. These alterations can be seen in infra-red reflectograms.
The face of the woman in the image The Old Guitarist is painted over. These marks would not usually be described as pentimenti as the subjects are totally different
Jacques de Norvins by Ingres
Caravaggio's The Cardsharps
Infrared is electromagnetic radiation (EMR) with wavelengths longer than that of visible light but shorter than microwaves. The infrared spectral band begins with waves that are just longer than those of red light, the longest waves in the visible spectrum, so IR is invisible to the human eye. IR is generally understood to include wavelengths from around 750 nm to 1 mm. IR is commonly divided between longer-wavelength thermal IR, emitted from terrestrial sources, and shorter-wavelength IR or near-IR, part of the solar spectrum. Longer IR wavelengths (30–100 μm) are sometimes included as part of the terahertz radiation band. Almost all black-body radiation from objects near room temperature is in the IR band. As a form of electromagnetic radiation, IR carries energy and momentum, exerts radiation pressure, and has properties corresponding to both those of a wave and of a particle, the photon.
This pseudocolor infrared space telescope image has blue, green, and red corresponding to wavelengths of 3.4, 4.6, and 12 μm, respectively.
Active-infrared night vision: the camera illuminates the scene at infrared wavelengths invisible to the human eye. Despite a dark back-lit scene, active-infrared night vision delivers identifying details, as seen on the display monitor.
Thermography helped to determine the temperature profile of the Space Shuttle thermal protection system during re-entry.
Infrared light from the LED of a remote control as recorded by a digital camera
