question: How do our eyes/mind decide on the luminance and the colour tempurature of the world around us?
comment: Our minds use a ton of contextual sense data subconsciously to create and project a consistent view of reality to our conscious mind. This dumbed-down version is very very fast, though sometimes not accurate. URL_0 In this famous image, the orange/brown center tiles are all the same color as the tile on the table in front.
passages: Section::::Early history (1850s–early 1970s).:Munsell.
  
  Albert Henry Munsell (1858–1918) is famous for inventing the Munsell color system, one of the first color order systems created. An American painter and art teacher at the Massachusetts Normal Art School, he had visited the tapestry works of Chevreul and studied color in France. With the use of his own unique inventions, including the Photometer that measures object luminance, Munsell started to determine color spaces and standardize the way color was organized and defined. 
   Section::::Physiology of color perception.:Cone cells in the human eye.
  
  A range of wavelengths of light stimulates each of these receptor types to varying degrees. The brain combines the information from each type of receptor to give rise to different perceptions of different wavelengths of light.
   Section::::Munsell color theory.
   Spillane and Sherlock introduced an expanded classification system, in which the four "seasonal" palettes were expanded to twelve.
  
  Veronique Henderson and Pat Henshaw
  
  Henderson and Henshaw combine the seasonal analysis method with a classification system based on contrasts in an individual's coloring, returning to the previous color study from Doris Pooser in the early 1990s.
  
  Section::::Systems of contrast analysis.
   Color constancy works only if the incident illumination contains a range of wavelengths. The different cone cells of the eye register different but overlapping ranges of wavelengths of the light reflected by every object in the scene. From this information, the visual system attempts to determine the approximate composition of the illuminating light. This illumination is then "discounted" in order to obtain the object's "true color" or reflectance: the wavelengths of light the object reflects. This reflectance then largely determines the perceived color.
  
  Section::::Physiological basis.:Neural mechanism.
   D. H. Foster (2011) states, "in the natural environment, the source itself may not be well defined in that the illumination at a particular point in a scene is usually a complex mixture of direct and indirect [light] distributed over a range of incident angles, in turn modified by local occlusion and mutual reflection, all of which may vary with time and position." The wide spectrum of possible illuminances in the natural environment and the limited ability of the human eye to perceive color means that color constancy plays a functional role in daily perception. Color constancy allows for humans to interact with the world in a consistent or veridical manner and it allows for one to more effectively make judgements on the time of day.
   Kruithof's findings may also vary as a function of culture or geographic location. Desirable sources are based on an individual's previous experiences of perceiving color, and as different regions of the world may have their own lighting standards, each culture would likely have its own acceptable light sources.
   Section::::Systems of contrast analysis.:Joanne Nicholson and Judy Lewis-Crum, "Color Wonderful" (1986).
  
  Another method of analysis was developed by color consultants Joanne Nicholson and Judy Lewis-Crum, whose 1986 book "Color Wonderful" explains their classification system, which is based on the amount of contrast in an individual's coloring.
  
  Section::::Systems of contrast analysis.:Alan Flusser, "Dressing the Man" (2002).
  
  Flusser lays out two relatively simple rules:
   Section::::Mathematics of color balance.:Von Kries's method.
  
  Johannes von Kries, whose theory of rods and three color-sensitive cone types in the retina has survived as the dominant explanation of color sensation for over 100 years, motivated the method of converting color to the LMS color space, representing the effective stimuli for the Long-, Medium-, and Short-wavelength cone types that are modeled as adapting independently. A 3x3 matrix converts RGB or XYZ to LMS, and then the three LMS primary values are scaled to balance the neutral; the color can then be converted back to the desired final color space:
   Color vision is how we perceive the objective color, which people, animals and machines are able to distinguish objects based on the different wavelengths of light reflected, transmitted, or emitted by the object. In humans, light is detected by the eye using two types of photoreceptors, cones and rods, which send signals to the visual cortex, which in turn processes those colors into a subjective perception. Color constancy is a process that allows the brain to recognize a familiar object as being a consistent color regardless of the amount or wavelengths of light reflecting from it at a given moment.
   There are various types of color systems that classify color and analyse their effects. The American Munsell color system devised by Albert H. Munsell is a famous classification that organises various colors into a color solid based on hue, saturation and value. Other important color systems include the Swedish Natural Color System (NCS), the Optical Society of America's Uniform Color Space (OSA-UCS), and the Hungarian Coloroid system developed by Antal Nemcsics from the Budapest University of Technology and Economics. Of those, the NCS is based on the opponent-process color model, while the Munsell, the OSA-UCS and the Coloroid attempt to model color uniformity. The American Pantone and the German RAL commercial color-matching systems differ from the previous ones in that their color spaces are not based on an underlying color model.
   The characteristic colors are, from long to short wavelengths (and, correspondingly, from low to high frequency), red, orange, yellow, green, blue, and violet. Sufficient differences in wavelength cause a difference in the perceived hue; the just-noticeable difference in wavelength varies from about 1 nm in the blue-green and yellow wavelengths, to 10 nm and more in the longer red and shorter blue wavelengths. Although the human eye can distinguish up to a few hundred hues, when those pure spectral colors are mixed together or diluted with white light, the number of distinguishable chromaticities can be quite high.
   Color balance is also related to color constancy. Algorithms and techniques used to attain color constancy are frequently used for color balancing, as well. Color constancy is, in turn, related to chromatic adaptation. Conceptually, color balancing consists of two steps: first, determining the illuminant under which an image was captured; and second, scaling the components (e.g., R, G, and B) of the image or otherwise transforming the components so they conform to the viewing illuminant.
   Comparisons of images balanced by diagonal transforms in a number of different RGB spaces have identified several such spaces that work better than others, and better than camera or monitor spaces, for chromatic adaptation, as measured by several color appearance models; the systems that performed statistically as well as the best on the majority of the image test sets used were the "Sharp", "Bradford", "CMCCAT", and "ROMM" spaces.
  
  Section::::Mathematics of color balance.:General illuminant adaptation.
   Section::::Research Methods.
   The advent of digital photography gave hope for better solutions to this problem. One of the earliest algorithms employed by Land and McCann in 1971 was Retinex, inspired by theories of lightness perception .This method is inspired by the eye’s biological mechanisms of adaptation when lighting conditions are an issue. Gamut mapping algorithms were also extensively studied in the context of color printing. Computational models such as CIECAM02 or iCAM were used to predict color appearance. Despite this, if algorithms could not sufficiently map tones and colors, a skilled artist was still needed, as is the case with cinematographic movie post-processing.
   Most digital cameras have means to select color correction based on the type of scene lighting, using either manual lighting selection, automatic white balance, or custom white balance. The algorithms for these processes perform generalized chromatic adaptation.
   In an attempt to move away from the complexities involved in seasonal color systems, some authors have suggested that it is possible to achieve attractive results by focusing instead on the level of contrast between a person's skin tone and his or her hair and eye colors.
  
  Section::::Systems of contrast analysis.:Donna Cognac, "Essential Colors".
   An analyst trained in this system relies on an in-person interview which reveals a range of clues. The most important indicators are the color, light, texture and pattern found in the skin, hair and eyes. Texture, color contrast levels, movement patterns, and facial and body characteristics are secondary indicators that help to determine basic seasonal type and subgroup within the season. Experienced practitioners also often observe predictable personality types and preferences that correspond to a person's seasonal group.
  
  BULLET::::- Winter
   1.Tint or hue, which mainly depends on dominate wavelength, displays the range of coloring, meaning that it identified the color position on the colorized circle.
  
  2.The luminance and lightness measure the relation of colors and light; dark or light features of the color base on the amount of light it reflects.
  
  3.Chroma or saturation correlates with the degree of tint; the majority aspect of highly saturated color is a pigment, and smooth colors constitute with low saturation.
  
  Section::::Advertisement's color.:Hypothetical background.
   The NCS states that there are six elementary color percepts of human vision—which might coincide with the psychological primaries—as proposed by the hypothesis of color opponency: white, black, red, yellow, green, and blue. The last four are also called unique hues. In the NCS all six are defined as elementary colors, irreducible qualia, each of which would be impossible to define in terms of the other elementary colors. All other experienced colors are considered composite perceptions, i.e. experiences that can be defined in terms of similarity to the six elementary colors. E.g. a saturated pink would be fully defined by its visual similarity to red, blue, black and white.
   The absolute luminance of the adapting field, which is a quantity that will be needed later, should be measured with a photometer. If one is not available, it can be calculated using a reference white:
  
  where "Y" is the relative luminance of background, the is the illuminance of the reference white in lux, "L" is the absolute luminance of the reference white in cd/m, and "Y" is the relative luminance of the reference white in the adapting field. If unknown, the adapting field can be assumed to have average reflectance ("gray world" assumption): .
   Light and color can influence how people perceive the area around them. Different light sources affect how the colors of walls and other objects are seen. Specific hues of colors seen under natural sunlight may vary when seen under the light from an incandescent (tungsten) light-bulb: lighter colors may appear to be more orange or "brownish" and darker colors may appear even darker. Light and the color of an object can affect how one perceives its positioning. If light or shadow, or the color of the object, masks an object's true contour (outline of a figure) it can appear to be shaped differently from reality. Objects under a uniform light-source will promote better impression of three-dimensional shape. The color of an object may affect whether or not it seems to be in motion. In particular, the trajectories of objects under a light source whose intensity varies with space are more difficult to determine than identical objects under a uniform light source. This could possibly be interpreted as interference between motion and color perception, both of which are more difficult under variable lighting.
   Color originates in the mind of the observer; “objectively”, there is only the spectral power distribution of the light that meets the eye. In this sense, "any" color perception is subjective. However, successful attempts have been made to map the spectral power distribution of light to human sensory response in a quantifiable way. In 1931, using psychophysical measurements, the International Commission on Illumination (CIE) created the XYZ color space which successfully models human color vision on this basic sensory level.
   Many Color Cards or palettes are created for various industries each year. For each area of focus a committee panel is formed, consisting of eight to twelve people, referred in the business as the "Color Czars." Each member of the committee performs their own research on what colors they feel will, should, dominate the next few years in that industry. The committee then convenes and they debate the merits of the member selections. In the end they choose 44 colors that will make it to the palette. According to Forecaster Ken Charbonneau, the process is a lot of debate before consensus.
  