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Proceedings Paper

Sharpness perception in defocused edges
Author(s): Hector Jorge Rabal; Elisa M. Colombo; Carlos Kirschbaum
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Paper Abstract

Physical parameters determining the perception of sharpness in defocused edges are searched for. A sensorial compression curve a gaussian model for the receptive fields and sensitivity to defocus are derived 1. METHODOLOGY AND RESULTS We search for significant physical parameters which determine the subjective perception of sharpness. Printed letters photographed with controlled defocusing were assessed by 7 observers according to a 7 steps scale of sharpness S (S low edge definition S10: high edge definition). Adaptation luminance was 100 cd/rn2. The density profile of the edges of the defocused letters was measured and after median window filtering the correlation coeficcients between its outstanding physical parameters and the psychophysical evaluation were calculated. Maximum and mean slope were found significant. The experimental values were then adjusted in a sensorial compression curv and its parameters calculated. From such a curve sensitivity to defocus was obtained. It was found that sensitivity is very small in both high and low sharpness sides and shows a maximum around the 6. 5 value (in a scale from 3 to 10) in perceived sharpness. Besides a gaussian receptive field model was proposed and its parameters calculated to adjust the sharpness response of the visual system to edges of arbitrary maximum slope and contrast. Two three and five gaussians were used for the receptive fields all results showing negligible differences. The edges were simulated by linear ramps and by exponentials.

Paper Details

Date Published: 1 July 1990
PDF: 1 pages
Proc. SPIE 1319, Optics in Complex Systems, (1 July 1990); doi: 10.1117/12.34752
Show Author Affiliations
Hector Jorge Rabal, Centro de Investigaciones Opticas (Argentina)
Elisa M. Colombo, Universidad Nacional de Tucuma (Argentina)
Carlos Kirschbaum, Universidad Nacional de Tucuma (Argentina)

Published in SPIE Proceedings Vol. 1319:
Optics in Complex Systems
F. Lanzl; H.-J. Preuss; G. Weigelt, Editor(s)

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