A method of calibrating a colorimeter arranged to measure light with a sensor arrangement providing n sensings with different spectral sensitivities, n being a number greater than or equal to four, wherein a sensing corresponds to the response of a sensor in the sensor arrangement, and to measure that light in the form of three primaries of a human-standard-observer-based color space, wherein one of the three primaries is an achromatic primary, the method comprising: - generating m sets of n sensings for m calibration illuminants with known values of the three primaries, wherein m is a number greater than n, - determining a first set of calibration factors that yields chromaticity-optimized values of the primaries when applied to signals measured by the n sensings, characterized in that the first set of calibration factors is determined by minimizing a norm of chromaticity distances of all calibration illuminants between (i) the chromaticity values retrieved by applying the first set of calibration factors to the signals measured by the n sensings, and (ii) known chromaticity values, and in that the method further comprises - determining a second set of calibration factors that yields an optimized value of the achromatic primary when applied to the signals measured by the n sensings, by minimizing a norm of achromatic distances between (i) values of the achromatic primary retrieved by applying the second set of calibration factors to the signals measured by the n sensings, and (ii) the known values of the achromatic primary, wherein light is measured by the colorimeter after the calibration by applying the first set of calibration factors to signals measured by the n sensings to obtain chromaticity-optimized tristimulus values and by applying the second set of calibration factors to these signals to obtain an optimized value of the achromatic tristimulus, and by scaling the chromaticity-optimized tristimulus values with a factor of the ratio of the optimized value of the achromatic tristimulus divided by the achromatic value of the chromaticity-optimized tristimulus values. - generating m sets of n sensings for m calibration illuminants with known values of the three primaries, wherein m is a number greater than n, - determining a first set of calibration factors that yields chromaticity-optimized values of the primaries when applied to signals measured by the n sensings, characterized in that the first set of calibration factors is determined by minimizing a norm of chromaticity distances of all calibration illuminants between (i) the chromaticity values retrieved by applying the first set of calibration factors to the signals measured by the n sensings, and (ii) known chromaticity values, and in that the method further comprises - determining a second set of calibration factors that yields an optimized value of the achromatic primary when applied to the signals measured by the n sensings, by minimizing a norm of achromatic distances between (i) values of the achromatic primary retrieved by applying the second set of calibration factors to the signals measured by the n sensings, and (ii) the known values of the achromatic primary, wherein light is measured by the colorimeter after the calibration by applying the first set of calibration factors to signals measured by the n sensings to obtain chromaticity-optimized tristimulus values and by applying the second set of calibration factors to these signals to obtain an optimized value of the achromatic tristimulus, and by scaling the chromaticity-optimized tristimulus values with a factor of the ratio of the optimized value of the achromatic tristimulus divided by the achromatic value of the chromaticity-optimized tristimulus values.