Textile color analyzer calibration

A spectrophotometer is operative to measure or analyze the colors of materials such as textiles. A test sample is held by a holder and is illuminated by polychromatic light. Diffuse light reflected from the sample is collected and converted to variable monochromatic light and detected. The system is calibrated by using a secondary white standard calibrated against a primary white standard, by using a black standard to compensate for dark current and internal reflectance from a pressure plate, and by using a mirror to obtain internal wall reflectance used in a correction factor.