In the imaging industries (Photography, Graphic Arts, and Graphic Design) D50 is the standardized source. D65 is used for color matching applications in the inks (but not ink on paper), paints, plastics, and textiles/apparel industries. In the imaging industry, D75 was used to help printers see the yellow ink of a process color print job and it is also the old daylight source for color matching applications. It is still used for some specialty applications (color vision testing for example). Most applications now require the use of either D50 or D65. GTI Graphic Technology, Inc. offers lamps in each of these color temperatures, in an assortment of sizes.
The “D” indicates it is a daylight simulator. The numerical value indicates the color temperature of the lamp (5000K for D50, 6500K for D65, and 7500K for D75).
CRI is the abbreviation for “Color Rendering Index.” It is a method of rating how well colors are rendered by a light source when compared to a standard theoretical source. A CRI of 100 means it will render colors very well. A CRI of 23 means it will not. For color assessment applications, a minimum CRI of 90 is required.
Yes. Color evaluation booths, used for imaging applications, should conform to ISO 3664:2009. This standard specifies the surround color of the booth, the light sources to be used, with their minimum color characteristics required, the light levels that are required on the viewing surface, and procedures. The daylight source is D5000, as specified by this standard, and is used for both reflective and transmissive art work.
Most all samples will appear differently under light sources having different color characteristics. A Blue source will accentuate blue colors and subdue reds and greens. A Red source will accentuate red colors, etc. This is called Inconstance. Two samples can match under different light sources but both still shift in color. Inconstance cannot be eliminated, only reduced using the proper mixture of dyes or pigments. It is very important to know it exists and observe its effect on the color of the sample to see if the inconstancy is overly objectionable. Keep in mind that a determining factor in color is the light source. If the source does not have Red energy, there will be no Red energy for the object to reflect and therefore will not appear Red.