Three-Dimensional Control of Color Management Systems - Control of Color Imaging Systems: Analysis and Design - page 349

The AR and VAR models can predict drift data accurately if the measured data
record length is large enough for estimation of the parameters of the models
(Equations 7.76 and 7.83). The accuracy of the model depends on the data length
as well as sensor noise. If the noise model of the color sensor is available, it can be
removed from the drift measurements of the printer, which can result in a more
accurate drift prediction.
7.5 GCR SELECTION AND INVERSION
In a four-color CMYK printer, as K increases, the total gamut volume created by
mixing CMY with K decreases (Figure 7.24). Gray component replacement (GCR)
provides a method to substitute black (K) for CMY mixtures in rendering a given color,
which results in an extension of the darker region of the gamut by changing lightness
FIGURE 7.24 (a) CMY gamut with K ¼ 0 (top), and K ¼ 255 (bottom). (b) CMY gamut
with K ¼ 0 (wire), K ¼ 153 (solid; middle), and K ¼ 255 (bottom). (c) CMY gamut with K ¼ 0,
51, 102, 153, 204, 255.