Colorimetry is one of the science knowledge that used to describe colors in numbers

For every person with normal sight, the concept of color is intuity and it is acquired by the infant at a very early age. Most frequently, color seems to be a property of the surface of objects, and enabling changes to be perceived - as in the riping of fruit, the quality of the products. In some cases, color does not belong to the surface but belong to the volume i.e blue color of the sky, the red of wine etc. And in other cases, color seems to a characteristic of the light emitted from the light sources, such as a bluish star, a cathode ray tube. For a human observer, a red object looks different from a white object object owing to the addition of a property to its surface. This is an error of our eye interpretation. We must remember that perceived color is associated with detection by receptors in the eye, followd by the interpretation in the brain, of the energy scattered or trasmitted by the material.

In 19th century, Eugene Chevreul said that "Color is within us". The used to descripbed how difficult to communicate color to simebody else. In linke manner, as Francois Parra likeed to recall "Color doesn't really exists!". He meant that only the material and light were phisically exist, and that color was a phenomenon of cerebral interpretation in the observer.

Color is a mystery. It is a bridge between the rational and irrational - in  the other word, it is between the exact science and human science.

Colorimetry is the technique of color measurement. We should remember that the measured color of an object is function of the light source, the material and the color responses of the observers in the brain. These data will be calcualted together and finallized with a set of 3 numerical colorimetric value, X, Y and Z. This extraordinary simplification constitues the fundamental fact of tricolor vision, called "trivariance"

Although visual trivariance was hit unpon long time ago by dyers and painters, who notice that three colors frequently sufficed to reproduced any color virtually, we used the genious of Thomas Young to explain it by the presence in the eye of three types of cone cell (Blue cone - which sensitives to the short wavelengths of the Spectrum, Green cones -  which sensitives to the medium wavelengths of the Spectrum, and the Red cone for the long wavelengths). Thomas Young's suggestion had been verified that colorimetry is the identication of color based on visual trivariance.

This make us know that the instrumental colorimetry is not at variance with the action in the eye, and that in fact it objectively completes the analysis of color achieved by man.

The majority of people in the color trade have now understood the adventage of "objective" mesurement of color. Debates have been done in the past for the subject of color, but with the new and modern colorimetric instrumentation, analysis and observation are converaging and agreeing.

For some decades past, we have known how to express a color in terms of its colorimetric values, describing the rightness, the hue, and the chroma. The measured color is a concrete, stable and easier to communicate.

The use of color measurement and the evaluation of color differences are decisive in the quality control of products, and so it was necessary to specify systems for the quantification of colorimetric diferrences leading to the acceptability of products.