We have studied in this paper the effect of the screen area illuminated or number of pixels used (with pixel-ratio-unity) on two possible models which in practice are used for producing and predicting colours specified by their coordinates (x, y, L). The first model provides the mixtures through the response curves (luminance versus DAC values) of the individual phosphorus; this is the most usual model used for CRT calibrations. The second model is calculated from the response curve of the achromatic (white) which is obtained by making the three DAC values equal.
