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Proceedings Paper

Gray-scale/resolution tradeoff
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Paper Abstract

Spatial resolution and grayscale resolution are two image parameters that determine image quality. In this study we investigate the trade-off between spatial resolution and grayscale in terms of the discriminability of steps, measured in bits, away from a standard image. A CRT display was used to simulate black-and-white images with a square-pixel geometry. Natural images and a test pattern consisting of a radially symmetric spatial frequency chirp of increasing radial frequency (called a zone plate) were studied. Multiple versions of each image were produced by varying the simulated pixel size and the number of gray levels and by filtering. Discrimination thresholds for pixel size and number of gray levels were measured for several locations in the parameter space of spatial resolution and grayscale resolution for each image. Unfiltered, low-contrast, Nyquist-filtered, and Gaussian-filtered versions of the images were studied. Resolution levels were always integer divisors of the CRT display resolution, produced by subsampling and pixel-replication. Gray levels were steps that were linear in luminance and that spanned the entire CRT luminance range. Discrimination thresholds were measured using a three-alternative forced-choice one-up-two-down double- random-staircase procedure. Simulation device limitations caused some measurements to be less precise than was desired.

Paper Details

Date Published: 1 May 1994
PDF: 13 pages
Proc. SPIE 2179, Human Vision, Visual Processing, and Digital Display V, (1 May 1994); doi: 10.1117/12.172697
Show Author Affiliations
Jennifer Gille, Western Aerospace Labs. at NASA Ames Research Ctr. (United States)
Ramin Samadani, Stanford Univ. (United States)
Russel A. Martin, Xerox Palo Alto Research Ctr. (United States)
James O. Larimer, NASA Ames Research Ctr. (United States)

Published in SPIE Proceedings Vol. 2179:
Human Vision, Visual Processing, and Digital Display V
Bernice E. Rogowitz; Jan P. Allebach, Editor(s)

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