Direct Interpretation of Colorimetric Readings in Terms of Colour Tolerance *

The practical use of any of the uniform colour co‐ordinate systems in colour‐tolerance work requires tedious and time‐consuming calculations. A simple and quick interpretation of the colorimetric colour difference of a production lot relative to a given standard value is desirable. This paper describes a graphical procedure by which this may be achieved, in particular for Colormaster readings interpreted in the Adams Chromatic‐Value system. For a given tolerance in N.B.S. units and for each colour standard, a graph is drawn and each production lot is plotted directly with reference to its RGB Colormaster readings. This plot provides ( a ) an immediate assessment of whether the lot is within the given tolerance and ( b ) a record of the colour‐tolerance performance in the production of the particular colour.