The Effects of Luminance Boundaries on Color Perception
Abstract
When a suprathreshold luminance flash, presented as an increment on a larger background field, accompanies a circular isoluminant chromatic flash at the same spatial location, chromatic threshold is reduced by about two-fold. This facilitation results from the clearly-visible edges of the luminance flash (the pedestal ) serving to demarcate the test region, segregating it from its surround. Recent signal detection experiments show that this facilitation does not occur as a result of the contour's reducing the spatio-temporal detection uncertainty of the observer; instead of merely directing the observer's attention, the pedestal must alter the properties of chromatic detectors (by changing the extent of spatial integration, for instance). A thin luminance ring can be used to create the facilitating contour. Displacing the ring relative to the test causes the facilitation to decline sharply, as if the visual system integrated uniformly within the demarcated region. However, the contour does not have to enclose the test region: small segments of the ring presented on the test circumference have about half the maximum facilitatory effect, while 180 deg of arcs produces the whole effect. These results can be used as a rigorous means of probing the way in which low-level visual attributes (edges, color) interact at higher levels.
Document Details
- Document Type
- Technical Report
- Publication Date
- Nov 15, 1989
- Accession Number
- ADA216741
Entities
People
- Charles F. Stromeyer Iii
- R. T. Eskew Jr.
- Richard E. Kronauer
Organizations
- Harvard University