Effect of Wavelength on Foveal Grating Acuity*

Abstract

Acuity-luminance relations for a grating test object were determined with red, yellow, green, and blue narrow-band chromatic illuminants for five subjects. At intermediate and high luminance levels, acuities for blue were lower than for the other chromatic illuminants in four of the five subjects. One of these subjects also showed lower asymptotic acuity for red at high luminances. The fifth subject, who did not show lower blue acuity, exhibited lower asymptotic acuities than the other subjects. The low blue acuities observed in four of the five subjects are attributed to neural rather than dioptric factors. INDEX HEADINGS: Vision; Color vision. ALTHOUGH many studies have investigated the effect of chromatic illuminants on foveal visual acuity, conflicting results have been obtained owing to differences of test object, psychophysical method, and degree of spectral purity of the illuminants used. In addition, the chromatic aberration of the eye is a complicating factor which has been treated in different ways by different investigators. Giorgi' in his study of the effect of wavelength on critical fusion frequency has pointed out that wavelength effects may be obscured by using broad-bandpass color filters. A similar observation on the effect of bandpass for acuity can be found in the data of Ferree and Rand, 2 who report lower acuity values for red and blue illuminants than for illuminants in the center of the visible spectrum. Desaturation of the red and blue stimuli improved acuity for these illuminants, but the absolute acuity levels reached with what the authors termed an equal-saturation spectrum remained lower for the red and blue. Chromatic aberration of the eye has been treated differently by different investigators. Some, wishing to minimize dioptric factors, have employed corrections for chromatic aberration at all wavelengths tested;;35 others, wishing to know how the visual system behaves in a natural environment, have not employed a correction for chromatic aberration. 2 '6 In several experiments, a corrective lens has been used only for the blue end of the spectrum. 7. 8 Under the latter conditions, the amount of accommodation required to focus the test object varies with the wavelength of illumination.

Psychophysics of reading IV Wavelength effects in normal and low vision

“…However, in the absence of a diffraction limitation, the results are inconsistent. Pokorny et al (1968) found lower acuity with narrow-band blue illumination than with green, yellow, or red illumination for four of five subjects. Nelson and Halberg (1979) found no color differences for contrast sensitivities measured with red, green, and achromatic gratings [cathode-ray tube (CRT) viewed through Wratten filters].…”

Enhancement of Contrast Sensitivity and Losses of Chromatic Discrimination with Tinted Lenses

“…The use of these filters by healthy subjects has been justified by an alleged increase of image contrast. This improvement may be attributed to a decrement of the chromatic aberration effects [11][12][13][14][15] , to a brightness increment 1,7,[16][17][18][19][20] , to scattering reduction 11,12,21 , or to a decrement of lenticular fluorescence [22][23][24] .…”

“…Since the VA, one of the tasks most sensitive to the presence of this aberration, is not improved with the use of tinted lenses, the effect of the reduction of chromatic aberration due to the lens probably will not improve the subject's performance in contrast discrimination tasks [11][12][13][14][15] . Nevertheless, it is likely that macula lutea and eye-lens fluctuations are enough to compensate reasonably the chromatic aberration of the eye 13 .…”

Effect of a yellow filter on brightness evaluated by asymmetric matching: measurements and predictions

“…Yellow filters are often recommended for activities, such as flying or skiing, requiring good performance in tasks involving contrast and luminance discrimination, depth perception and spatial resolution. But, although there is evidence in the literature supporting the conjecture that yellow filters improve the performance of these visual tasks (Wright 1949, Campbell and Gubisch 1967, Kislin et al 1968, Pokorny et al 1968, Clark 1969, Luria 1972, Miller 1974, Reading and Weale 1974, Sivak and Bobier 1978, Lermann 1980, Kinney et al 1983, Yap 1984, Bockelmann 1987, Dees and Lyle 1989, Kelly 1990, Rieger 1992, Provines et al 1992, Chung and Pease 1993, Rabin and Wiley 1996, Provines et al 1997, Wolffsohn et al 2000, de Fez et al 2002, evidence to the contrary also abounds (Aarnisalo 1987, Allen 1964a, Clark 1968, Ginsburg and Nelson 1978, Kelly et al 1984, Leguire and Suh 1993, Lynch and Brilliant 1984, Thomas and Kuyk 1988, Verriest 1963, Wyszecki 1956.…”