Color photography in the context of "Colors"

Color (or colour in Commonwealth English) is the visual perception produced by the activation of the different types of cone cells in the eye caused by light. Though color is not an inherent property of matter, color perception is related to an object's light absorption, emission, reflection and transmission. For most humans, visible wavelengths of light are the ones perceived in the visible light spectrum, with three types of cone cells (trichromacy). Other animals may have a different number of cone cell types or have eyes sensitive to different wavelengths, such as bees that can distinguish ultraviolet, and thus have a different color sensitivity range. Animal perception of color originates from different light wavelength or spectral sensitivity in cone cell types, which is then processed by the brain.

Colors have perceived properties such as hue, colorfulness, and lightness. Colors can also be additively mixed (mixing light) or subtractively mixed (mixing pigments). If one color is mixed in the right proportions, because of metamerism, they may look the same as another stimulus with a different reflection or emission spectrum. For convenience, colors can be organized in a color space, which when being abstracted as a mathematical color model can assign each region of color with a corresponding set of numbers. As such, color spaces are an essential tool for color reproduction in print, photography, computer monitors, and television. Some of the most well-known color models and color spaces are RGB, CMYK, HSL/HSV, CIE Lab, and YCbCr/YUV.

Hand-colouring (or hand-coloring) refers to any method of manually adding colour to a monochrome photograph, generally either to heighten the realism of the image or for artistic purposes. Hand-colouring is also known as hand painting or overpainting.

Typically, watercolours, oils, crayons or pastels, and other paints or dyes are applied to the image surface using brushes, fingers, cotton swabs or airbrushes. Hand-coloured photographs were most popular in the mid- to late-19th century before the invention of colour photography, and some firms specialized in producing hand-coloured photographs.

Subtractive color or subtractive color mixing predicts the spectral power distribution of light after it passes through successive layers of partially absorbing media. This idealized model is the essential principle of how dyes and pigments are used in color printing and photography, where the perception of color is elicited after white light passes through microscopic "stacks" of partially absorbing media, allowing some wavelengths of light to reach the eye and not others. It is also a concept seen in painting, wherein the colors are mixed or applied in successive layers, though predicting realistic results (such as blue and yellow mixing to produce green instead of gray) requires more complex models such as Kubelka–Munk theory.

Monochrome photography is photography where each position on an image can record and show a different amount of light (value), but not a different color (hue). The majority of monochrome photographs produced today are black-and-white, either from a gelatin silver process, or as digital photography. Other hues besides grey can be used to create monochrome photography, but brown and sepia tones are the result of older processes like the albumen print, and cyan tones are the product of cyanotype prints.

As monochrome photography provides an inherently less complete reproduction than color photography, it is mostly used for artistic purposes and certain technical imaging applications.

Louis Arthur Ducos du Hauron (8 December 1837 – 31 August 1920) was a French pioneer of color photography.

Dye coupler is present in chromogenic film and paper used in photography, primarily color photography. When a color developer reduces ionized (exposed) silver halide crystals, the developer is oxidized, and the oxidized molecules react with dye coupler molecules to form a dye in situ. The silver image is removed by subsequent bleach and fix processes, so the final image will consist of the dye image.

Dye coupler technology has seen considerable advancement since the beginning of modern color photography. Major film and paper manufacturers have continually improved the stability of the image dye by improving couplers, particularly since the 1980s, so that archival properties of images are enhanced in newer color papers and films. Generally speaking, dye couplers for paper use are given more emphasis on the image permanence than those for film use, but some modern films (such as Fujichrome Provia films) use variants of couplers that were originally designed for paper use to further improve the image permanence.