Standard Depth Scales. As the fastness of dyeing depends on the depth of colour it is necessary to specify standard depths when making comparisons. Dye manufacturers pattern cards refer to these depths in fastness ratings for their products. SDC standard depths are illustrated in a range of 6 steps each from 2/1 to 1/25 depth over a range of 18 hues plus 2
navies and 2 blacks.

Standards
ISO 105-A01, AATCC EP4, BS 1006