Rods affect S-cone discrimination on the Farnsworth–Munsell 100-hue test

Knight, Roger; Buck, Steven L.; Fowler, Garth A.; Nguyen, Anh Q.

doi:10.1016/s0042-6989(97)00414-8

Cited by 20 publications

(21 citation statements)

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“…25 We suggest, therefore, that rod influences may not impair chromatic discrimination in the near periphery of the visual field (e.g., Ͻ 3.5°). The reported impairment of tritan scores on the FM-100 hue test, 10 where presumably foveal viewing was also used, is entirely consistent with a selective loss of chromatic sensitivity along the tritan axis at low light levels. The authors find that error scores along the tritan axis increase systematically as the light level decreases and this is consistent with the results of this study (see Figs.…”

Section: S40mentioning

confidence: 54%

“…5 The selective loss of chromatic sensitivity, along the blue-yellow axis is also consistent with the finding of tritan errors for the FM-100 Hue test, when performed under low illumination. [7][8][9][10] Closer examination of thresholds along the blue-yellow axis at low light levels raises the question of whether rod influences on chromatic mechanisms either contribute to the observed increase in thresholds or cause the threshold asymmetry along a tritan axis. Figure 5 shows a comparison of chromatic thresholds measured 3.5°in the periphery, on the cone plateau region of the dark-adaptation curve, where rod influences should be absent, and after full dark adaptation to the same background level, where rod influences should be maximal.…”

Section: S40mentioning

confidence: 99%

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Measurements of chromatic sensitivity in the mesopic range

et al. 2000

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We measured chromatic threshold sensitivity in the mesopic range using a combination of techniques that mask the detection of photopic and scotopic luminance contrast signals. The measurements were carried out at a number of light levels in the range 45-0.004 cd/m 2 , both foveally and with the stimulus centered 3.5°in the periphery. In order to investigate the effect of rod signals on chromatic detection thresholds in the near periphery of the visual field, we measured chromatic threshold ellipses when fully dark-adapted and during the cone plateau region of the dark-adaptation curve. The results confirm a number of previous observations and reveal new findings:reduction in background adaptation causes a loss of chromatic sensitivity that becomes more rapid as one enters the mesopic range. This loss is observed both foveally and in the near periphery and cannot, therefore, be attributed entirely to rod intrusion. A small increase in chromatic thresholds is observed in the near periphery when compared with foveal measurements. Comparison of foveal and peripheral measurements also reveals a tilt in the orientation of the major axis of the chromatic threshold ellipse away from the tritanopic towards the deuteranopic colour confusion line: • The loss of chromatic sensitivity is not uniform, with the tritan axis being most affected. The ellipticity (i.e., the ratio of major to minor axis of the ellipse plotted on the CIE 1976, UCS diagram) can increase by as much as a factor of two, as the light level decreases from 10 -0.056 cd/m 2 . • At lower light levels, some subjects show an asymmetry in chromatic thresholds along the tritan axis. This asymmetry is consistent with greater sensitivity to increases than decreases in S-cone excitation. • Measurements of chromatic sensitivity following either complete dark-adaptation or during the cone plateau phase of the dark-adaptation curve yield essentially the same results. These findings, therefore, suggest that rod signals have little or no influence on chromatic sensitivity at this eccentricity.

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Section: S40mentioning

confidence: 54%

Section: S40mentioning

confidence: 99%

Measurements of chromatic sensitivity in the mesopic range

et al. 2000

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“…Under dark adaptation, rods contribute to color perception (e.g., Stabell & Stabell, 1998). The contribution of rods and their interaction with cones affect color sensitivity (e.g., Zele, Kremers, & Feigl, 2012;Knight, Buck, Fowler, & Nguyen, 1998;Stabell & Stabell, 2002). Since rods contribute nonlinearly to color discrimination (e.g., Zele et al, 2012), their contribution results in a different profile of JNDs in comparison with JNDs for photopic vision (Knight et al, 1998).…”

Section: Discussion (Discrimination)mentioning

confidence: 99%

Categorical sensitivity to color differences

2013

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Categorical perception provides a potential link between color perception and the linguistic categories that correspond to the basic color terms. We examined whether the sensory information of the second-stage chromatic mechanisms is further processed so that sensitivity for color differences yields categorical perception. In this case, sensitivity for color differences should be higher across than within category boundaries. We measured discrimination thresholds (JNDs) and color categories around an isoluminant hue circle in Derrington-Krauskopf-Lennie (DKL) color space at three levels of lightness. At isoluminant lightness, the global pattern of JNDs coarsely followed an ellipse. Deviations from the ellipse coincided with the orange-pink and the blue-green category borders, but these minima were also aligned with the second-stage cone-opponent mechanisms. No evidence for categorical perception of color was found for any other category borders. At lower lightness, categories changed substantially, but JNDs did not change accordingly. Our results point to a loose relationship between color categorization and discrimination. However, the coincidence of some boundaries with JND minima is not a general property of color categorical boundaries. Hence, our basic ability to discriminate colors cannot fully explain why we use the particular set of categories to communicate about colors. Moreover, these findings seriously challenge the idea that color naming forms the basis for the categorical perception of colors. With respect to previous studies that concentrated on the green-blue boundary, our results highlight the importance of controlling perceptual distances and examining the full set of categories when investigating category effects on color perception.

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“…In trichromatic observers, rod activity has been shown to impair both constant-luminance Rayleigh discrimination thresholds 9 and S-cone mediated discrimination on the Farnsworth-Munsell 100-Hue Test. 10 However, rod activity has been shown to improve wavelength discrimination in S-cone monochromats. 11 The basis for this difference between normal and color-deficient observers is not known.…”

Section: Introductionmentioning

confidence: 99%

Stimulus size affects rod influence on tritan chromatic discrimination

Knight¹,

Buck²,

Pereverzeva³

2000

Color Res. Appl.

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A signal-detection procedure was used to measure the influence of rods on S-cone-mediated ("tritan") chromatic discrimination in normal trichromatic human observers. Rod influence on discriminability of both increments and decrements in S-cone excitation was assessed by comparing cone-plateau (minimizes rod influence) and dark adapted (maximizes rod influence) conditions. For 1°stim-uli, rods impaired tritan discrimination, especially for Scone decrements. For 8°stimuli, rods had no systematic effects. This confirms that rods have the same direction of effect (impairment) on tritan discrimination as has been shown for Rayleigh (L-M) discrimination. However, the size dependence of the rod effect on tritan discrimination is opposite to that previously shown for either Rayleigh discrimination or hue appearance. This provides further evidence for separable rod influences on S-cone and L-M cone pathways.

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Rods affect S-cone discrimination on the Farnsworth–Munsell 100-hue test

Cited by 20 publications

References 18 publications

Measurements of chromatic sensitivity in the mesopic range

Measurements of chromatic sensitivity in the mesopic range

Categorical sensitivity to color differences

Stimulus size affects rod influence on tritan chromatic discrimination

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