What are Color & Color difference assessments?

Color is not a physical reality; and different people perceive color differently. Generally, when asked what color a certain object is, some may reply with subjective responses, such as ‘light blue’, ‘rich dark purple’ or ‘bright gold’ which may differ from individual to individual.

With advances of technology, color specification has become a precise science by specifying a thread & fabric color quantitatively as a number. It improves the understanding of color and the color matching process.

What is color?

It is not a simple answer, since color is not a physical reality. It is a psychological response by an individual to the different wavelengths of radiant energy. Hence, color can be described as the appearance of an object which is an interpretation of sensations detected by the eye.

Color difference assessment?

A reliable method of assessing color difference is very important. Incorrect color could lead to rejection, which means unnecessary loss of time and money.

There are two ways to assess the color:

• Visual assessment 
  Instrumental measurement

 Visual Assessment:

In visual assessment viewing conditions are extremely important if the right judgements are to be made. The following points should be taken into consideration while visually assessing color:

• The level of illumination must be sufficient to produce cone (photopic) vision
• The illumination should be a good simulation of one of the CIE standard illuminants
• The nature of the background against which the sample is viewed must be controlled; the background should be a neutral grey color such as Munsell N5 or N7.
• The field of view should be controlled. If the panels are of different size or shape, then a mask should be cut from thin grey card and placed over the panels so that equal areas of the two panels are in view
• The two panels should be positioned side by side, with no gap between them.
• Always position the standard on the same side of the pair, usually the left hand side.
• Allow a few moments for the eye to become adapted to the ambient illumination in the lighting cabinet before viewing the color difference panels
• If highly chromatic panels have been viewed, then allow a few minutes for the eye to readapt to neutral before judging the next pair of panels

Instrumental Measurement:

The spectrophotometer can measure the reflectance values of standard as well as batch of any object. These values can be converted into color difference values using CIELAB and CMC mathematical equations.

Reference: www.coatsindustrial.com