Color Matching Experiment Research Articles

Tutorial on color science

The principles of tristimulus colorimetry are presented in tutorial fashion. The classic color matching experiments are described with an emphasis on the assumptions that are implicit in these tests and on the units of measure which should be used to record the results. The transformation to alternative sets of primaries is derived and the geometry of the resulting color spaces is illustrated. An annotated bibliography of relevant literature is also provided.

Spectral sensitivity of single cones in the retina of Macaca fascicularis.

Colour vision depends on the wavelength-dependent absorptions of three different photolabile pigments each located in a particular type of retinal cone. The spectral absorption of primate cones has been examined by microspectrophotometry, but this method gives information only at wavelengths where the absorption is relatively strong. Here we have analysed the absorption of two of the cones over a wider range of wavelengths by recording their electrical responses to monochromatic light. The observations were made on the retina of the monkey Macaca fascicularis, an animal thought to have cone pigments like those of man. The measured spectral sensitivities of the red-sensitive ('red') and green-sensitive ('green') cones agreed well with estimates of the cone pigment absorptions derived from colour-matching experiments in humans. At long wavelengths the sensitivity of the red cones was found to decline more rapidly than that of the green. This behaviour, attributable to the cone pigment molecules themselves, explains the paradoxical hue shift, in which a light of very long wavelength is perceived to be identical to a light of shorter wavelength.

New color-matching ellipses.

Three new sets of color-matching experiments have been made by three observers binocularly viewing a bipartite field (each half subtending 3°) of a three-primary colorimeter. Each set of color-matching data refers to 28 test colors scattered over the chromaticity gamut provided by the colorimeter. The luminance of each test color was 12 cd · m−2; the white surround (subtending 40°) was maintained at 6 cd · m−2. The elliptical cross sections (for Y = const) of the observed color-matching ellipsoids are compared with results previously published by MacAdam, and Brown and MacAdam. In view of the inherent experimental uncertainties of data of this kind, the new color-matching ellipses correlate well with those obtained by Brown, and Brown and MacAdam, but show significant deviations from those obtained by MacAdam’s observer P. G. Nutting, Jr. The discrepancies are puzzling. A note of caution is added with regard to the usefulness of color-matching ellipses in testing line elements. A set of color-matching ellipses can reveal only little of the visual mechanism that governs the precision of color matching and its assumed direct correlation with judging small color differences. It appears that fundamentally different line elements can reproduce almost equally well a given set of color-matching ellipses.

S-potential sources as excitation pools

The dependence of the electrical responses of single elements of L- and RG-types on the excitation of different receptor types has been studied in several species of freshwater fishes. By colour matching and adaptation experiments the L-cells as well as RG-cells are shown to be always connected with two types of receptors having sensitivity maxima at 530 and 620 mμ. The amplitude of the L-response (taking into account only the stable potential deflection), is the sum of deflections corresponding to the excitation of each receptor type alone. Certain effects of red background observed on RG-cells, namely the polarity-reversal of response to the red test light, the rise of blue response and the shift of the neutral point, are also shown to follow from summation of signals from different receptors and selective suppression of the different receptors by coloured backgrounds. This conception of the summation of signals from different receptors in S-potential can also explain Tomita's (1963) observation of the increase of negative red response in the triphasic cell induced by a violet background, which produces a negative response as well.

Color Determination of Simultaneously Excited Broad- and Narrow-Band Phosphors

The emission spectra of color television picture tubes which contain both rare earth and sulfide phosphors have been recorded on a spectroradiometer. The recording reveals that the simultaneous excitation of the two types of phosphors produces narrow-band spectra that are superimposed on a continuous spectrum. In this paper, a typical spectrum obtained from the excitation of narrow-band yttrium vanadate and broad-band sulfide phosphors is shown, and the details of the chromaticity analysis are given. In the analysis of a recorded spectrum of this type, a weighting factor must be applied to the line spectra. This factor is a function of the bandpass of the exit slit of the recording spectroradiometer. The validity of the technique is corroborated by the results of color matching experiments on color television picture tubes that contain only broad-band emitting sulfide phosphors.