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Proceedings Paper

Psychophysical thresholds and digital camera sensitivity: the thousand-photon limit
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Paper Abstract

In many imaging applications, there is a tradeoff between sensor spatial resolution and dynamic range. Increasing sampling density by reducing pixel size decreases the number of photons each pixel can capture before saturation. Hence, imagers with small pixels operate at levels where photon noise limits image quality. To understand the impact of these noise sources on image quality we conducted a series of psychophysical experiments. The data revealed two general principles. First, the luminance amplitude of the noise standard deviation predicts threshold, independent of color. Second, this threshold is 3-5% of the mean background luminance across a wide range of background luminance levels (ranging from 8 cd/m2 to 5594 cd/m2). The relatively constant noise threshold across a wide range of conditions has specific implications for the imaging sensor design and image process pipeline. An ideal image capture device, limited only by photon noise, must capture at least 1000 photons/pixel (1/sqrt(103) ~= 3%) to render photon noise invisible. The ideal capture device should also be able to achieve this SNR or higher across the whole dynamic range.

Paper Details

Date Published: 23 February 2005
PDF: 10 pages
Proc. SPIE 5678, Digital Photography, (23 February 2005); doi: 10.1117/12.587468
Show Author Affiliations
Feng Xiao, Agilent Technologies (United States)
Joyce E. Farrell, Stanford Univ. (United States)
Brian A. Wandell, Stanford Univ. (United States)

Published in SPIE Proceedings Vol. 5678:
Digital Photography
Nitin Sampat; Jeffrey M. DiCarlo; Ricardo J. Motta, Editor(s)

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