A new approach to the assessment of standard depth

Standard depth is a term used to describe a subjectively defined property of colour, yet it is of great importance both in fastness testing and standardisation of dyes. In this paper, analysis of a large number of databases from the four major European dye manufacturers resulted in a new method of determining 1/1 standard depth for each angle round the hue circle. The definition holds whether the colour is dull or bright in shade. After allowance is made for the colour of the substrate the lightness at the point of maximum chroma ( L* at C* max ) has been found to be remarkably constant for a specified hue. An equation relating L* at C* max to hue angle round the hue circle has been obtained and is suggested as the basis of a method of defining 1/1 standard depth.