There are three major classes of color measuring instruments used in the textile industry: colourimeters, 0/45° and 45/0° geometry spectrophotometers, and integrating sphere geometry spectrophotometers. Colourimeters were early pioneers but have limitations as they cannot separate pure color from appearance or detect color changes under different light sources. Reflectance spectrophotometers measure the amount of light reflected at different wavelengths to produce a reflectance spectrum, which can be used to calculate CIE XYZ values. They illuminate samples with white light and calculate reflected light levels at 31 wavelength intervals using a monochromating device. Main components are a light source, optical system, light dispersing system, detector, and