Colors match when their tristimulus values agree, which can happen with quite different spectra. Shading a sheet with a different dye set from the customer's master, or matching a brightened sheet to an unbrightened one, often gives a pair that agrees under D65 but splits under shop lighting or incandescent lamps. Color labs check matches under two or three illuminants to catch it before shipping.
Matches in the light booth on daylight, flips red under the A lamp, classic metamerism from the new dye.
Match a customer's sample with the same dye family they used wherever possible; the closer the spectra, the fewer surprises under store lighting.
Also heard as
- illuminant metamerism
- metameric failure
Related terms
Delta E
Single number for the total color difference between a sample and its target, usually in CIELAB units.
Shade
The exact color of a paper grade measured against its approved standard, for whites as well as tinted sheets.
Shading dye
Small dose of blue or violet dye used to cancel the yellow cast of a white sheet and steer its tint.
Illuminant D65
Standard CIE daylight at about 6500 K, with enough ultraviolet to excite optical brighteners strongly.