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Journal of the Optical Society of America A

Journal of the Optical Society of America A

| OPTICS, IMAGE SCIENCE, AND VISION

  • Vol. 16, Iss. 5 — May. 1, 1999
  • pp: 979–986

Visual sensitivity in the presence of a patterned background

Alan W. Freeman and David R. Badcock  »View Author Affiliations


JOSA A, Vol. 16, Issue 5, pp. 979-986 (1999)
http://dx.doi.org/10.1364/JOSAA.16.000979


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Abstract

The sensitivity of the visual system depends on ambient illumination: Sensitivity is reduced in the presence of a bright, uniform background. We asked how sensitivity is adjusted when the background is spatially detailed and therefore contains both luminance peaks and troughs in the neighborhood of a foreground object. A test flash was superimposed on a static sinusoidal grating. As the grating’s spatial frequency increased, sensitivity for flash detection declined, regardless of whether the flash was superimposed on a peak or a trough of the grating. We studied the mechanisms underlying this loss of sensitivity by delivering the test stimulus through one eye and the background through the other. The conclusion is that three mechanisms are involved. Luminance adaptation and a masking process adjust sensitivity at low- and mid-range spatial frequencies, respectively. The third mechanism, a contrast gain control, is localized (it occurs at spatial frequencies approaching the limit for resolution) and fast (complete in half a second), and it results from early processing in the visual pathway (it is absent during dichoptic viewing). This local adjustment of sensitivity may help to protect the clarity of even the smallest details in the visual scene.

© 1999 Optical Society of America

OCIS Codes
(330.1800) Vision, color, and visual optics : Vision - contrast sensitivity
(330.5510) Vision, color, and visual optics : Psychophysics
(330.6100) Vision, color, and visual optics : Spatial discrimination
(330.7320) Vision, color, and visual optics : Vision adaptation

History
Original Manuscript: September 4, 1998
Revised Manuscript: January 4, 1999
Manuscript Accepted: January 11, 1999
Published: May 1, 1999

Citation
Alan W. Freeman and David R. Badcock, "Visual sensitivity in the presence of a patterned background," J. Opt. Soc. Am. A 16, 979-986 (1999)
http://www.opticsinfobase.org/josaa/abstract.cfm?URI=josaa-16-5-979

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