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In color science the perception of colors is divided as the interaction of three different, independent elements:

The two first elements can be described in pure physical terms, the light source by its spectral intensity distribution, the object by its reflectance spectrum i.e. the fraction of light intensity reflected within a certain spectral region. The observer imposes limitations since the electrical signals generated at the eye are processed in the brain through an unknown process into the final color sensation. Here lies the psychochromatic origin of color sensation, a point that we always must bear in mind when dealing with color assessment.

Color science distinguishes also two different steps approaching color assessment. Both operation are supported in the software:

Colorimetric analysis

Color quantification or colorimetric analysis is quite straightforward; the problem posed by the observer is solved by defining an average observer through experimentally determined response functions. Color quantification relies on a number of conventions and definitions given by the CIE (Commission Internationale de lEclairage) that form the basis for color quantification and communication. Any color can be characterized by three numbers, the set of all possible triples define a certain color solid that contains all possible colors detected by the human eye. Depending on the system used to quantify color the three numbers have different names, in general one can say that a color can be characterized by its saturation, its hue and its luminosity. After the reflectance values of samples have been measured, they are weighted with those of a light source and of the observer leading to saturation, hue and luminosity (or lightness). Two colored samples with exactly the same values for the color coordinates are said to be equivalent and they are perceived as equal by the eye under observation conditions. Bear in mind however that a change in illumination conditions will lead to different color coordinates and the color coordinates of color samples may change in different extent and not be equivalent under the new conditions (they are said to build a metameric pair).

Color models

There are a lot of color models or color spaces described in literature. A few of the most commonly used color models also used in the software have been described in the following:

Colorimetric analysis report

The following information are calculated for the final colorimetric analysis report:

Color comparison

Color differences or color comparison is a pure industrial problem and can be stated as to which extent color coordinates of two samples can differ and still be assessed as the same by the trained eye; this is the typical color matching problem. There are many formulas to express color differences but none of them has universal character i.e. they must be calibrated to the color region where assessment is conducted.

Color comparison are available under consideration of the following color models:


Color theory