Visual Shift
Color match variation occurs when two fabric samples appear to match under one light source but differ under another. This illuminant metamerism is caused by different dye formulations that create identical visual sensations under daylight but have different spectral reflectance curves. When the light source shifts to store lighting, the difference is exposed.
This is a common cause of color rejections in retail shops.
Dye Selection
Colorists must choose dyes with similar spectral properties to prevent color mismatches across light sources. If the laboratory uses different dyes for the body fabric and the ribbed trim, illuminant metamerism will make the two parts look like different colors in a store even if they matched in the lab. The spectrophotometer checks the color difference under three standard light sources including daylight, incandescent, and fluorescent lamps.
Spectral Control
Software algorithms predict the likelihood of shade mismatching by calculating a metamerism index for every dye recipe. A low index means the color match remains stable under different lights. This is why brands set a maximum limit on this index for all approved batches.
The mill must adjust the recipe if the index is too high.
Inspection Procedure
Quality inspectors use specialized light boxes to compare dyed fabric. The inspector cycles through the light settings to search for illuminant metamerism. If a mismatch is found, the batch must be redyed.
