Patent ID: 8125687

Claim:
A method for determining colorant values for color patches in a printable target that contains plural such color patches, wherein the printable target is printable by a color printer having multiple colorant channels including a black channel and multiple non-black channels, and wherein the printable target is thereafter usable for color characterization of the color printer, wherein the method comprises: printing a black ramp using the black channel; measuring color values of the black ramp to obtain measured color values thereof; selecting substantially uniform steps on the black ramp as determined in a printer independent color space, by applying principal component analysis (PCA) to the measured color values or color values derived from the measured color values of the black ramp, and by using a first principal component from PCA thereof to select the substantially uniform steps, wherein the substantially uniform steps are substantially invariant to small variations in the first principal component of the measured color values on the black ramp; performing, for multiple ones of the substantially uniform steps on the black ramp, the following steps (a) through (c) of: (a) printing a chromatic ramp using each of the multiple non-black colorant channels along with the black channel at a corresponding black level of the one of the substantially uniform steps on the black ramp; (b) measuring color values of the chromatic ramps to obtain measured color values thereof; (c) selecting substantially uniform steps on each of the chromatic ramps as determined in a printer independent color space, by applying principal component analysis (PCA) to the measured color values or color values derived from the measured color values of each such chromatic ramp, and by using a first principal component from PCA thereof to select the substantially uniform steps, wherein the substantially uniform steps are substantially invariant to small variations in the first principal component of each such chromatic ramp, and wherein there are a greater number of substantially uniform steps on each such chromatic ramp at smaller values of the black level than number of substantially uniform steps on each such chromatic ramp at larger values of the black level; and populating colorant values of the color patches in the printable target by using multiple combinations on the substantially uniform steps on the black ramp and on the chromatic ramps that meet an ink limiting threshold.