In a color printer calibration process, a color printer is driven with a set of printer signals selected to print a set of color samples throughout a printer gamut. A color measuring device measures the colorimetric response at each sample, to derive a mapping of printer signals to colorimetric responses of the printer. From the colorimetric responses, a preprocessing step is used to increase the number of measurements, using linear interpolation between local responses whereby the number of colorimetric responses to be mapped is increased. Then, a lookup table mapping colorimetric values to printer signals is generated, at regular intervals throughout the printer gamut, to produce a regular interval set of interpolated colorimetric values, derived from the measured colorimetric values and the linearly interpolated values using a distance-weighted averaging method. The look up table is stored in a color conversion memory for use in converting color definitions from a first color space to the printer color space.