Surfaces of uniform visual depth were mapped in L*a*b* colour space, at six levels of depth, from visual assessments made by a panel of professional colourists employed in the dye manufacturing industry. By interpolation, the surfaces of uniform visual depth at depths corresponding to the average of the ISO standard depths were determined. The algorithms developed enable the determination of the L* value that a colour of any hue or chroma should have in order for it to correspond to one of the standard depths. © 2006 The Authors. Journal compilation © 2006 Society of Dyers and Colourists.