Second-site adaptation in the red-green chromatic pathways

Stromeyer, C.F.; Cole, Graeme R.; Kronauer, Richard E.

doi:10.1016/0042-6989(85)90116-6

Cited by 125 publications

(66 citation statements)

References 43 publications

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“…The eye is not a very good detector of absolute changes in luminance over an extended time scale (1 h) or spatial extent. Also, it has been shown that chromatic pathways adapt very quickly, so small changes in relative cone quantal catch rates may not affect the results of measured thresholds (Stromeyer, Kronauer, & Cole, 1985). However, significant changes may be observable at a "second site" and these may affect the results, regardless of the slow time course of the change.…”

Section: Warm-up Characteristicsmentioning

confidence: 99%

Calibration of a color monitor for visual psychophysics

Metha

Vingrys

Badcock

1993

Behavior Research Methods, Instruments, & Computers

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It has become common for stimuli used in visual psychophysical experiments to be presented on high-resolution color cathode-ray tubes (CRTs) such as the Barco CDCT 6551. These enable a flexibility of color, spatial-frequency content, temporal-frequency content, duration, size, and position that is not provided by most other media. CRTs are, however, not perfect; they suffer from the effects of temporal instability, spatial variability, lack of phosphor constancy, gun interdependence, and gun nonlinearity. This paper describes methods of assessing these aspects of monitor performance with respect to how significant each may be in psychometric terms. Although every application of CRT use in visual psychophysics is different, some general rules can be formulated to help ensure that unwanted effects are kept to a minimum. For the CRT used in this study (Barco CDCT 6551), a warm-up time of 30-45 min is necessary before chromatic and luminous stability ensues. Restriction of individual gun outputs to within 10%-90% of the possible range ensures that the effects of gun interdependence and lack of phosphor constancy are negligible. Calibration methods dealing with the linearization of gun output are also discussed.CRT (cathode-ray tube) technology offers a unique opportunity to display a variety of visual stimuli. The advantages offered by CRTs over other media include flexibility of color, size, position, and presentation duration as well as spatiotemporal frequency content of the stimuli. A major disadvantage of the CRT is that the maximum light output achievable is limited, compared with other display techniques such as Maxwellian view. This is still well into the photopic range, as is borne out by observing that images are in fact colored on CRT screens. Color CRTs have three channels, so it is possible and desirable to describe their output in terms of a mixture of three independent primaries, although, as will be shown, strict independence is not achieved. In order to determine the limitations that may exist in applying CRTs to the study of the human visual system, we have undertaken a thorough study of the colorimetric aspects of a Barco CDCT 6551 monitor that was used in our laboratory. We believe that this high-resolution color monitor is likely to be used in other laboratories and that the information provided in this paper will be useful to others. Moreover, the techniques described here can be applied to other brands and models of CRTs and should provide a useful reference for those unfamiliar with this technology or colorimetry. 1This work was supported byARC Grant A79030414 andNH& MRC Grant 890568 to A.J.Y. We thank George Smith for his consultation and helpful comments on the manuscript. We also thank two anonymous reviewers for their very useful comments. Address correspondence toA. Metha, Department ofOptometry, University ofMelbourne, Parkville YIC 3052, Australia.In the present study, we consider several aspects of monitor performance: temporal stability, spatial variability, phosphor constancy, gun i...

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Section: Warm-up Characteristicsmentioning

confidence: 99%

Calibration of a color monitor for visual psychophysics

Metha

Vingrys

Badcock

1993

Behavior Research Methods, Instruments, & Computers

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“…The amount of the phase shift depends on wavelengths, since for a fixed spatial frequency the beam separation at the corneal surface For any grating spatial frequency, we let the constants T L and Tc represent contrast threshold for gratings that stimulate each mechanism alone. We can write the mechanism responses in terms of the contrasts C L and C c seen by each mechanism and of these contrast thresholds: RL = CL/T L and R c = Cc/T c. We allow the contrast thresholds for each mechanism to depend' on grating spatial frequency, but we assume that the spectral responsivity of each mechanism is independent of this spatial frequency.53, 54 We also assume that the response of each mechanism does not depend on the spatial phase of the grating.…”

Section: Effect Of Head and Eye Movements On The Relative Phase Of Inmentioning

confidence: 99%

Aberration-free measurements of the visibility of isoluminant gratings

1993

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We developed a new apparatus and psychophysical technique to extend isoluminant contrast-sensitivity measurements to high spatial frequencies. The apparatus consists of two identical laser interferometers that are designed to produce phase-locked two-color interference fringes on the retina without the influence of diffraction and most aberrations in the eye. However, even with interferometry, transverse chromatic aberration of the eye can produce a wavelength-dependent phase shift in the interference fringes, which can be exaggerated by head movements. To reduce the effect of head movements, isoluminant red and green interference fringes of equal spatial frequency and orientation were drifted slowly in opposite directions to guarantee a purely isochromatic (in phase) and a purely isoluminant (out of phase) stimulus during each cycle of stimulus presentation. With this technique we found that observers could resolve red and green stripes at spatial frequencies higher than 20 cycles per degree (c/deg) (20-27 c/deg), substantially higher than has previously been reported. This places a lower bound on the sampling density of neurons that mediate color vision. At all spatial frequencies, even those above the isoluminant resolution limit, a relative phase of the red and the green components could be found that obliterated the appearance of luminance modulation at the fringe frequency. Above the resolution limit, red-green-isoluminant interference fringes are seen as spatial noise, which may be chromatic aliasing caused by spatial sampling at some stage in the chromatic pathway.

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“…1B). The red-green chromatic mechanism (Thornton & Pugh, 1983;Stromeyer et al 1985) responds to an equally weighted difference of L and M cone-contrast, IcL' -dM'I, where c = d. At threshold IcL' -dM'I = constant, so red-green detection thresholds should form lines of unit slope in (L', M') space (Fig. 1B).…”

Section: Moving Gratings: Detection and Direction Identificationmentioning

confidence: 99%

“…At each velocity, motion thresholds were measured for many red-to-green amplitude ratios. The motion thresholds are plotted as detection contours in two-dimensional co-ordinates of L cone contrast versus M cone contrast (Stromeyer, Cole & Kronauer, 1985. Different segments of the contours suggest the presence of a luminance and a spectrally opponent motion mechanism that respond, respectively, to the sum and the difference of the L and M cone-contrast signals.…”

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confidence: 99%