Glass Filters for Checking Performance of Spectrophotometer-Integrator Systems of Color Measurement

A set of five specially selected colored-glass filters to identify variables of malfunction of photoelectric recording spectrophotometers equipped with tristimulus integrators have been standardized on a number of spectrophotometers corrected for all known errors (wavelength, zero, 100 percent, slit-width, inertia, back-reflectance, and stray-energy). To these standardized spectrophotometric data definite amounts of these errors were deliberately introduced and converted to tristimulus values and chromaticity coordinates of the International Commission of Illumination system of colorimetry for Sources A, B, and C. Similar reductions show the effects of slit widths of 1, 5, 10, and 15 millimicrons (mµ) on computed results both by the selected-ordinate method of 10, 30, and 100 ordinates, and by the weighted-ordinate methods of 1-, 5-, 10-, and 15-mµ intervals. Duplicate sets of these glasses have been evaluated by visual comparison with this set of master standards, and are available as part of the Standard Materials Program of the National Bureau of Standards. By comparing the certified values of luminous transmittance and chromaticity coordinates for a set of these glasses with the values obtained on a particular integrator-spectrophotometer combination, the type and extent of instrumental errors may be evaluated.