Jo Ann S. Kinney

Factors affecting induced color

Abstract The amount of color induced into a field of Illuminant A was determined for four inducing colors, red, yellow, green and blue, by having observers compare the induced color with a field of actual colored light. The results, given in C. I. E. values, show that the amount of color induced increases as the size of the inducing field is increased, as the luminance ratio between inducing and induced fields is increased, and, to a small extent, as the purity of the inducing color is increased.

Comparison of Scotopic, Mesopic, and Photopic Spectral Sensitivity Curves

Spectral sensitivity curves have been established for the ten-degree periphery throughout a range of intensities from absolute scotopic threshold to a level five log units above threshold. Surround conditions included adaptation of the eye both to complete darkness and to the light level under investigation. In addition, foveal curves have been established at one level under the same experimental conditions as the peripheral curves.The results show that there is no large shift in the curves toward the longer wavelengths with increasing intensity until a level five log units above threshold has been reached, and that, even at this point, the peripheral curve does not approach the spectral sensitivity found in the foveal curve. While the curves retain the predominant scotopic element, that is, sensitivity to the shorter wavelengths remains basically unchanged, sensitivity to the longer wavelengths does increase throughout the entire range of intensities investigated. This is true for both surround conditions; in addition, a slight increase in sensitivity to the long wavelengths and better brightness discrimination are found with the lighted surround.

Sensitivity of the Eye to Spectral Radiation at Scotopic and Mesopic Intensity Levels

Spectral sensitivity curves were established for three intensity levels above scotopic threshold with a two-degree field placed ten degrees from fixation against a dark surround. These curves were compared with the minimum scotopic luminosity curve determined for the same retinal position for each observer. The results showed that (1) there is a range of intensities over which relative spectral sensitivity does not change appreciably from the scotopic luminosity function, (2) there are irregularities in these mesopic curves which may be attributed to cone activity, and (3) the first change in spectral sensitivity with increased intensity is found in the long-wavelength half of the spectrum.

Reaction Time to Spatial Frequencies Using Yellow and Luminance-Matched Neutral Goggles

ABSTRACT The popularity of yellow goggles for outdoor activities has long been a paradox to visual scientists as previous tests of their effectiveness have failed to show any visual advantage. The achromatic/chromatic theory of color vision suggests a possible solution to the paradox which was tested by measuring reaction times to spatial frequencies of varying contrast. Reaction times were faster with yellow goggles than with luminance‐matched neutrals under certain conditions. These conditions included frequencies in the middle of the range of human sensitivity and, specifically, the lower contrasts of these frequencies. The theoretical and practical applications of the results are discussed.

EFFECT OF STIMULUS SIZE, DURATION, AND RETINAL LOCATION UPON THE APPEARANCE OF COLOR

The names given to spectral stimuli from 480 to 610 mμ and to a white-light test stimulus were obtained using 11′ or 21′ diam stimulus fields, exposed for 20 msec in the fovea and for 20 and 200 msec at 5° and 10° in the periphery. The experiment was designed to test the hypothesis that normal color vision is replaced by tritanopic vision in all parts of the retina if the total luminous energy is sufficiently reduced. The results obtained with four observers confirm the presence of tritanopia when small brief stimuli are viewed foveally but fail to confirm it in the periphery. Rather, reduced color vision in the periphery is more nearly characteristic of deuteranomaly which ends ultimately in colorless vision. These results are discussed as giving support to the notion that foveal tritanopia is due to the depressed sensitivity of the blue receptor mechanism found in the central fovea.

Appearance of Color for Small, Brief, Spectral Stimuli, in the Central Fovea*

While color-vision characteristics of tritanopia (blue–yellow deficiency) are well known to occur with small fields in the central fovea, the possibility of similar confusions as a function of brief duration has previously only been suggested. The problem has been investigated in this study by determining the color names given by nine color-normal and two deuteranopic observers to spectral stimuli from 565 to 590 mμ and to a white light. The test stimuli, all presented foveally, subtended diameters of 54, 21, and 11 min at durations of 200 and 20 msec. For stimuli presented at small subtense and short duration, green was sometimes seen as blue or blue–green, a neutral band was found in the yellow–green (570–580 mμ), and no confusion was found between reds and greens. The degree of tritanopic-like color confusions in the fovea is related to both the exposure time and the size of the test area. The results are discussed in relation to the foveal vs small-field characteristics of apparent tritanopia.

Visibility of colors underwater.

The underwater visibility of various colors, both fluorescent and nonfluorescent, was measured in four different bodies of water. The waters were selected to sample the continuum from very murky to clear. SCUBA divers observed with a horizontal path and other subjects on the surface looked down vertically. Fluorescent colors were always more visible than nonfluorescent, but the specific colors that were easiest and most difficult to see depended upon the body of water.

Effect of Field Size and Position on Mesopic Spectral Sensitivity

Spectral sensitivity curves were determined at mesopic luminance levels, 0.1 and 0.01 ft-L, for a 2° field viewed foveally and parafoveally. These data are compared with similar curves for a 10° field, centrally fixated, whose area encompasses the smaller areas studied individually. The results show that, at 0.1 ft-L, differences between the 2° and 10° fields are similar to those between the CIE 2° and 10° photopic curves; furthermore the large field data can be predicted from the 2° data. At 0.01 ft-L however the spectral sensitivity is different from both CIE photopic and scotopic values at all positions and summation within the large field is complex.

Seasonal Changes in Scotopic Sensitivity

The scotopic sensitivity of three subjects was tested weekly over the course of a year. In addition, two measures were made to indicate each subject’s amount of exposure to sunlight. Scotopic sensitivity was found to be poorest in the summer months, when exposure to sunlight was greatest, and to increase gradually during the fall and winter. The course of sensitivity over the year agreed well with the external measures of exposure to sunlight, the best single measure being the amount of “blue” light reflected by the skin.

Visual evoked responses elicited by rapid stimulation

Abstract An assessment of the technique of eliciting VERs with rapid rates of stimulation has revealed that differences in evoked response due to stimulus parameters may be minimized under these conditions. The probable reason is that addition of ongoing activity from one flash to that elicited by another occurs; this addition can obscure or enhance wave form differences present in the complete evoked response. A comparison of visual-evoked responses (VERs) to rapid flash rates which were empirically determined with VERs synthesized from a linear addition of the first two segments of the complete evoked response reveals a rather remarkable agreement in most cases. On the other hand, some failures to predict empirical data in this manner to occur. These failures are not due to temporal variations and their etiology is unknown at this time. Until the electrogenesis of the VER is understood, we conclude the use of both a fast and a slow rate to obtain VERs is a good methodological technique for studying brain functioning.