Jove
Visualize
Contact Us
JoVE
x logofacebook logolinkedin logoyoutube logo
ABOUT JoVE
OverviewLeadershipBlogJoVE Help Center
AUTHORS
Publishing ProcessEditorial BoardScope & PoliciesPeer ReviewFAQSubmit
LIBRARIANS
TestimonialsSubscriptionsAccessResourcesLibrary Advisory BoardFAQ
RESEARCH
JoVE JournalMethods CollectionsJoVE Encyclopedia of ExperimentsArchive
EDUCATION
JoVE CoreJoVE BusinessJoVE Science EducationJoVE Lab ManualFaculty Resource CenterFaculty Site
Terms & Conditions of Use
Privacy Policy
Policies

Related Experiment Videos

Contrast overconstancy.

M A Georgeson1

  • 1Department of Psychology, University of Bristol, UK.

Journal of the Optical Society of America. A, Optics and Image Science
|March 1, 1991
PubMed
Summary
This summary is machine-generated.

In parafoveal vision, high-frequency gratings appear higher than expected, a phenomenon termed "overconstancy." This occurs near visual thresholds and is explained by a model of contrast coding with specific parameters.

Related Concept Videos

You might also read

Related Articles

Articles linked to this work by shared authors, journal, and citation graph.

Sort by
Same author

The temporal properties of first- and second-order vision.

Vision research·2000
Same author

Motion contrast: a new metric for direction discrimination.

Vision research·2000
Same author

Spatial resolution and receptive field height of motion sensors in human vision.

Vision research·2000
Same author

Adaptive filtering in spatial vision: evidence from feature marking in plaids.

Perception·2000
Same author

Feature matching and segmentation in motion perception.

Proceedings. Biological sciences·2000
Same author

Does early non-linearity account for second-order motion?

Vision research·1999
Same journal

Phase retrieval with prior information.

Journal of the Optical Society of America. A, Optics and image science·2008
Same journal

Clinical microscopy of the cornea utilizing optical sectioning and a high-numerical-aperture objective.

Journal of the Optical Society of America. A, Optics and image science·1993
Same journal

Eye-tracking laser Doppler velocimeter stabilized in two dimensions: principle, design, and construction.

Journal of the Optical Society of America. A, Optics and image science·1993
Same journal

Effects of aging in retinal image quality.

Journal of the Optical Society of America. A, Optics and image science·1993
Same journal

Axial eye-length measurement by wavelength-shift interferometry.

Journal of the Optical Society of America. A, Optics and image science·1993
Same journal

Fractal analysis of steady-state-flicker visual evoked potentials: feasibility.

Journal of the Optical Society of America. A, Optics and image science·1993
See all related articles

Area of Science:

  • Visual perception
  • Neuroscience
  • Image processing

Background:

  • Contrast constancy is observed in foveal vision above threshold.
  • Contrast sensitivity varies with spatial/temporal frequencies and luminance.
  • Parafoveal vision shows different contrast perception characteristics.

Purpose of the Study:

  • Investigate contrast perception in parafoveal vision.
  • Identify and explain the phenomenon of 'overconstancy'.
  • Develop and validate a model for contrast coding in parafoveal vision.

Main Methods:

  • Used two experienced observers to assess contrast perception.
  • Tested gratings at high spatial frequencies (12-18 c/deg) and near threshold.
  • Applied a mathematical model R' = [(C-T)/(Cnorm-T)]m to fit data.

Related Experiment Videos

Main Results:

  • High-spatial-frequency gratings appeared higher in contrast in parafoveal vision (overconstancy).
  • Overconstancy was most pronounced at high spatial frequencies and near threshold.
  • The proposed contrast coding model accurately described the observed data.

Conclusions:

  • Overconstancy in parafoveal vision is linked to changes in contrast response compression (m) with spatial frequency.
  • The model incorporates threshold subtraction, nonlinear compression, and normalization.
  • Parafoveal contrast perception deviates from foveal constancy, especially at higher spatial frequencies.