value y f which may be equal to or different from the initial value y i thus each complete calibrated curve is a combination of two partial curves the partial curves may have the same or different functions for example a complete calibrated hue and saturation curve may have an in portion that is a function of an ease equation and an out portion that is a function of the modified kulbelka monk absorption equation discussed above moreover the partial curves may have the same or different parameters that define the actual shape of the partial curves for example a complete calibrated hue and saturation curve may have an in portion that has an overall parabolic shape and an out portion that has an overall logarithmic shape in light of the foregoing and once the ink set is chosen the grayscale of each ink in the ink set should be calibrated or linearized from 0 ink saturation the ground color to full or 100 saturation calibration is often necessary because ink printed on a fibrous substrate such as fiber containing paper and fabric has a tendency to proceed very quickly from a perceived 0 saturation to a perceived 100 saturation in fact when a grayscale band is printed without calibration 90 or more of that grayscale band is usually perceived as being 100 saturated however for accurate printing a grayscale band must proceed smoothly from a perceived 0 saturation to a perceived 100 saturation where only about 1 of that grayscale band is 100 saturated.