The colour difference between the two measurements is then calculated for each sample and these are
plotted as a function of ink film thickness. The “best fit” straight line through these points is then drawn as
shown in Figure B.2 and the slope of the line calculated. (Alternatively, the regression coefficient may be
calculated directly from the data.) The reciprocal of this value is then computed and is the transparency
measurement value, T. Using the graphical method this value may be calculated directly as follows