Factors Affecting Instrumental Measurement and Visual Assessment of Colour Differences

The factors affecting the instrumental measurement of colour differences are reviewed. For most types of sample the performance of modern instruments is more than adequate provided that sufficient care is taken. Problems may arise with metameric pairs and fluorescent samples. The main source of error lies in the colour–difference equations/ this is quite separate from errors due to the instrument. Problems associated with visual assessments are discussed. The use of a panel of three observers will produce more reliable results and may be preferable under certain circumstances.