“…A calibration model G can be written as y = G͑w , d͒, where y is tone values on paper, w is sensor measurements from on-board densitometers, and d is uncontrollable but measurable factors/disturbances collected in life test, such as temperature, humidity, and throughput. 8 The tone values y are the measured reflectances of the reproduced color patches printed at the designated half-tone levels. In this study, a tone value is defined as the Euclidian distance ͑⌬E͒ in CIE L ء a ء b ء space 9 between the color point of a primary color printed at a particular half-tone level and the substrate color.…”