The Sensation of Color

Color measurement n. Color is a manufactured object is normally obtained by applying a colorant (dye or pigment) to al polymer substrate, such as textile, paper or paint medium. The appearance of such surface colors depends on (1) the nature of the prevailing illumination, (2) the interaction of the illuminating radiation with the colored species in the surface layers, and (3) the ability of the radiation that is transmitted, reflected and scattered from the colored surface to induce the sensation of color in the human eye/brain system. Color measurement consists of the physical measurement of light radiated, transmitted, or reflected by a specimen under specified conditions, and mathematically transformed into standardized colorimetric terms, which can be correlated with visual evaluations of colors relative to one another. McDonald R (ed) (1997) Colour physics for industry, 2nd edn. Society of Dyers and Colourists, West Yorkshire, England. Physical and chemical examination of... 

Photopic fot- 6-pik adj [NL photoplay fr. phot- + -opia] (1915) An adjective used to describe vision mediated by the cone receptors in the retina of the eye, which give rise to the sensation of color occurring at high and medium levels of luminance. (Stedman s medical dictionary, 27th edn. Lippincott Williams Wilkins, New York, 2000)... 

There has been a great deal of investigation of the anatomy and physiology of the brain as it relates to color perception, based on an array of techniques that continues to expand. The primary visual input arrives in the striate cortex at the back of the head in addition, there are several other brain centers that receive visual input, some of which seem specifically concerned with chromatic vision. The meaning of this activity for visual perception is not yet clear. In particular, it is not yet known exactly which kinds or patterns of activity immediately underly the sensation of color or exactly where they are located in the brain. 

Subjective Description of Color in Terms of Equivalent Stimuli. The observer, unable directly to measure or describe a color sensation in absolute terms, is able to evaluate it in terms of certain stimuli which produce an equivalent sensation. Subjectively the comparison is accomplished experimentally with a colorimeter, so designed that the color of the sample is seen in one half of a photometric field and the mixture of color produced by independently controllable components is seen in the other half. By proper adjustment of the components, a unique setting will be found which produces a match in the photometric field and the color of the sample can be specified in terms of the amounts of the chosen components. 

Blurred vision. Three hypnotic subjects responded positively to this condition two hypnotic subjects and the simulator responded with schizoid withdrawal. Those that responded positively responded in terms of the primacy of color and light over form, and compared their perceptions of the world with impressionist paintings. One subject and the simulator responded in terms of an inability to make contact with anybody the last subject responded with a blunting and dulling of thought processes. All subjects lost some sensation in non-visual modalities. When the perception of outlines alone was blurred, colors tended to stand out. Alan Watts (1962) has noted how the perception of form and the perception of color may really be the same, but the behavior patterns of these subjects do not support this point of view. 

The colorant varies, from one preparation to another, in its degree of dispersion, as demonstrated by the amounts that can be removed from solutions by various filtration or defecation techniques. In the case of the colorant associated with raw sugars, the degree of dispersion varies with the method of preparing the solution. This suggests that the impurities causing the twin, visual sensations of color and turbidity are closely related, and may, in fact, be the same materials. 

The sensation of sound is a thing sui generis, not comparable with any of our other sensations. No one can express the relation between a sound and a color or smell. Directly or indirectly, all questions connected with this subject must come for decision to the ear, as the organ of hearing and from it there can be no appeal. But we are not therefore to infer that all acoustical investigations are conducted with the unassisted ear. When once we have discovered the physical phenomena which constitute the foundation of sound, our explorations are in great measure transferred to another field lying within the dominion of the principles of Mechanics. Important laws are in this way arrived at, to which the sensations of the ear cannot but conform. 

Color is a very important parameter for many manufactured products including paint, cosmetics, foods, beverages, pharmaceutical liquids and tablets, textiles, and so on. If the calcium supplements in a bottle are snpposed to be pink, aU the tablets in the bottle should be the same color. All of the bottles in a lot shonld be the same color. If they are not, consumers may think there is something wrong with the tablets. Both the generation and sensation of color are complex and depend... 

The latest of the five treatises discussed here is entitled The Science of Color by the Committee on Colorimetry of the Optical Society of America (1953). A slight letdown is possibly inevitable, which a rereading does not entirely banish. The report is designed to include an elementary discussion to attract and hold the attention of casual readers, with a gradual transition to more advanced exposition. The food technologist tackling the psychophysics of color is apt to be impatient when confronted with distinctions between operational and relational definitions. He learns that the use of quantitative concepts would specialize the relational definitions in an undesirable manner loc. cit, p. 220). Continued study makes the reader more aware of the problems facing the Committee. Is color to be defined as a sensation or in terms of perception How many attributes of color are to be admitted ... 

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