Predicting the colour of trichromatic prints by measuring the colour o
f the primaries and their areas has been shown to be possible using la
rge area textile prints. This approach has been extended to paper prin
ting with much smaller coloured areas, in a predetermined array of squ
ares. As before, the light reflected from the coloured areas mixed add
itively within the integrating sphere of a spectrophotometer. Cyan, ma
genta, and yellow were used with the addition of red, green, blue, and
black, to simulate the typical situation likely to arise in commercia
l paper ink-jet printers, Partitive colour-mixing theory was used to p
redict the colours, and the results compared well with those obtained
by measurement. However, unwanted overlaps of the printed coloured squ
ares caused all the measured results to be darker and of higher chroma
. The reverse process, whereby the area of each colour was calculated
for a given target colour, specified by its tristimulus values, was al
so carried out. The results were generally used to produce the target,
within one square out of 16. (C) 1998 John Wiley & Sons, Inc.