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Color rendering

Color rendering is the numeric expression of how a color looks like under a lighting source compared with how it looks like under a reference source.  
The system universally used up to now to measure the color rendering of a source is CRI (Color Rendering Index), based on the average survey of 8 colors. Since the arrival of LED, it was shown that such system is inadequate as the 8 colors used to obtain the CRI are low saturated; as a consequence, when a source does not have a complete emitting spectrum, saturated colors may result insufficient.
The CIE (Commission internationale de l'éclairage) has been declaring for a few years that the system was no longer sufficient after the arrival of LED and requested to create new methods to have more realistic and trustworthy values as one number was no longer enought to represent the charcteristics of a source. Many systems were proposed (CQS, CAM, etc.) to extract data that give a more precise idea of the color rendering characteristics of a source. 
Nowadays the more complete and reliable system is thought to be TM-30-15 whish is no longer based on 8 colors but rather on a table of 99 (CES), including the colors of nature, skin, fabrics, plastics, paints, etc. Such colors selcted from the real world are more representative and reliable, so the result is much more accurate.
The values emerged by this new method are basically two.
1.     TM-30-15 Fidelity Index:Rf
  • - Check of the color fidelity compared with a reference source
  • - System similar to CIE Ra but much more precise thanks to a higher quantity of colors used to calculate the average (99 rather than 8)
  • - Score from 0 to 100 without possibility to use negative measures
  • - Equal importance to every movement, in any direction.

2. TM-30-15 Gamut Index:Rg
  • - A value lower than 100 indicates an average decrease in color saturation.
  • - A value higher than 100 indicates an average increase in color saturation.
Rf and Rg values achievable
Values achievable in measurements are identified with the following limits:
  • - minimum Rf 0, maximum Rf 100
  • - minimum Rg 60, maximum Rg 140