M. L. F. de Mattiello

Saturation scales for surface colors

Abstract Magnitude estimations of saturation were obtained for each of 15 pigmented surfaces of different hue, viewed under artificial light in a 4° test field. Saturation was found to be related to colorimetric purity by a power function whose exponent varied with the dominant wavelength. The highest exponents were in the yellow-orange region and the lowest in the blues. Five of the color samples were viewed under both daylight and artificial light with test fields of 4° and 0.7°. The larger visual field and daylight gave somewhat lower exponents for all dominant wavelengths except those in the yellow region. The exponents for saturation of surface colors are systematically higher than those reported for aperture colors.

Saturation constancy in surface colors

The level of reflectance of pigmented surfaces observed in daylight affects saturation growth in different ways, depending on the wavelength of the samples. Numerical and matching judgments collected in previous experiments were replotted in families of monochromatic (constant hue) saturation power functions for blue, green, yellow, and red. For each hue the set of functions intersected at a point at which the colorimetric purity and saturation were invariant with reflectance. The points of intersection were: blues, 0.081 colorimetric purity (Pc) and 2.7 cromes; greens, 0.257 Pc and 4.6 cromes; yellows, 0.694 Pc and 8.3 cromes; and reds, 0.144 Pc and 3.6 cromes. A straight line fitted to these four intersecting points makes it possible to interpolate other intersecting points for other hues. Two additional experiments were designed to compare a function of saturation with a function of lightness for a set of different hues (heterochromatic functions). Observers judged saturation in one experiment and lightness in the other. Lightness grows linearly with reflectance, and saturation increases as the 0.5 power of Pc, suggesting a different perceptual discrimination for the two dimensions. The relation between changes in quantity and percentage of color perceived was tested in an additional experiment. Observers assigned the following saturation values to the samples with Pc close to the converging points: 13% of color for blues, 20% for reds, 25% for greens, and 40% for yellows.

Saturation of colored samples at various levels of reflectance

The dependence of saturation on the level of reflectance of colored surfaces was measured by numerical estimation and by matching judgments. Four sets of chromatic samples, one for each hue--blue, 460 nm, green, 510 nm, yellow, 580 nm, and red, 620 nm--within a range between 4% and 65% reflectance, were presented to the observers. The largest changes of saturation were observed at the high and low values of reflectance. The effect is more pronounced for the yellows than for the reds and greens, and relatively less apparent for the blues. For each hue, saturation grows faster at intermediate values of reflectance. The four families of saturation functions permitted us to draw a map of equal-purity contours. There are values of colorimetric purity for which saturation remains constant for all levels of reflectance.

Validity of Different Contrast Tests in Glaucoma

The present study investigated (a) the correlations between different periodical and aperiodical contrast tests as applied to glaucoma, and (b) their performance with reference to the conventional visual acuity and perimetry tests.

Change in the Inhibiting Effects of Ocular Pathology

The capacity to analyze luminous stimuli under contrast conditions was tested using sixty patients with retina, glaucoma, nerve and amblyopia diseases. It is demonstrated that the inhibitory effect produced when a luminous background surrounds a center test, is altered during the ocular diseases until it disappears. These results are discussed in relation to previous psychophysical and electrophysiological observations.

Fusion chromatic and temporal frequencies in normal and anomalous observers

The red-green chromatic and temporal fusion time required by normal and color-deficient observers was compared by means of red-green chromatic pulses of constant luminosity. The data obtained demonstrate the possibility of a new temporal test of acquired color vision defects.

Retinal and cortical sensitivity to different chromatic stimuli

By applying the color-naming psychophysical method and a Wright colorimeter, a chromatic sequence produced by the mixture of different quantities of red-green and blue-yellow is described. Retinal mixtures are produced monocularly in the classical manner. When interaction at the cortex is desired, a dichoptic channel is added to the colorimeter. This channel can be adjusted to the observer’s interpupillary distance in order to superpose the stimuli in the two eyes. The data obtained show a clear difference between cortex and retina that fundamentally affects chromatic variables.

A clinical evaluation of the lightness and contrast vision tests

18 cases of Glaucoma, 20 of Retinal diseases, 15 of Optical nerve diseases and 15 of Ambloyopia, were studied. The results of both tests are analyzed for statistical significance, and the possibility of using the tests for diagnostic differentiation is evaluated.

The Function of Chromatic Lightness and its Application in Ocular Pathology

Completing a set of previous tests in which the visual luminosity and contrast functions were analyzed, this paper will mainly verify the chromatic luminosity function, following the intramodal matching method, using one scale of 55 greys and four chromatic scales of constant saturation: blue, yellow, red and green.

Saturation Contrasts: Clinical Application Potential

The method of magnitude estimation was used to analyze chromatic edge detection produced by isoluminant stimuli. Observers quantified the visibility of edges produced by six different pairs of hues at variable saturation. When the data were plotted on log-log coordinates, negative and positive power functions were obtained. Correlations were observed between their exponent values and color vision model of spectrally opponent cells.