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Color By Numbers: Using a Calibration Source Spectrally Matched To Your Test Source Is Key To Measurement Accuracy

Published

Author(s)

Steven W. Brown, Yoshihiro Ohno

Abstract

The measurement of color (called colorimetry) uses a set of three spectral response curves standardized by the Commission Internationalede l'Eclairage (CIE) that approximate the human visual response. It turns out that the accuracies of color measuring instruments canvary significantly, depending on the spectra of the colors measured. In the case of tristimulus colorimeters, the mismatch of the relativespectral responsivities of the individual channels to the CIE color matching functions is a source of error when different spectraldistributions are measured. If you measure an artifact with the same spectral distribution as the calibration source, measurement errorstend to be canceled out and the uncertainty will be small. However, if you want to measure the color of artifacts having very differentspectral distributions from illuminant A, e.g. displays, LEDs, discharge lamps, etc., the error analyses can be complex, requiringknowledge of both the source spectral distribution and the spectral response of each of the colorimeter filter channels. In most cases, thisinformation is not available to the user, and the uncertainties in color measurements are not well known and errors are often much larger than expected. For these applications, additional care must be taken to understand and reduce the measurement uncertainty. The National Institute of Standards and Technology has established calibration services for colorimeters (and spectroradiometers) to be used in display measurements, as well as for photometric and colorimetric measurements of standard LEDs. These artifacts should assist laboratories in analyzing and reducing uncertainties in their colorimetric measurements.
Citation
Color By Numbers: Using a Calibration Source Spectrally Matched To Your Test Source Is Key To Measurement Accuracy

Keywords

color matching functions, colorimeter, colorimetry, tristimulus colorimeter, uncertainty

Citation

Brown, S. and Ohno, Y. (2002), Color By Numbers: Using a Calibration Source Spectrally Matched To Your Test Source Is Key To Measurement Accuracy, Color By Numbers: Using a Calibration Source Spectrally Matched To Your Test Source Is Key To Measurement Accuracy (Accessed April 23, 2024)
Created February 1, 2002, Updated February 17, 2017