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The perception of static colored noise: detection and masking described by CIE94

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Author: Lucassen, M.P. · Bijl, P. · Roelofsen, J.
Type:article
Date:2008
Institution: TNO Defensie en Veiligheid
Source:Color Research and Application, 3, 33, 178-191
Identifier: 19025
doi: doi:10.1002/col.20401
Keywords: Vision · Chromatic discrimination · CIE94 color difference · Detection threshold · Noise masking · Psychophysics · Image recognition · Sensory perception · Spurious signal noise · Chromatic discrimination · Detection threshold · Noise masking · Color · colour

Abstract

We present psychophysical data on the perception of static colored noise. In our experiments, we use the CIE94 color difference formula to quantify the noise strength and for describing our threshold data. In Experiment 1 we measure the visual detection thresholds for fixed pattern noise on a uniform background color. The noise was present in one of three perceptual color dimensions lightness (L*), chroma (C*), or hue (h). Results show that the average detection threshold for noise in L* is independent of hue angle and significantly lower than that for noise in C* or h. Thresholds for noise in C* and h depend on hue angle in an opponent fashion. The measured detection thresholds, expressed in terms of the components ?L*/kLSL, ?C*/kCSC, and ?H*/kHSH that build up the CIE94 color difference formula are used to tune CIE94 to our experimental conditions by adjusting the parametric scaling factors kL, kC, and kH. In Experiment 2, we measure thresholds for recognizing the orientation (left, right, up, down) of a test symbol that was incremental in L*, C*, or h, masked by supra-threshold background noise levels in L*, C*, or h. On the basis of the CIE94 color difference formula we hypothesized (a) a constant ratio between recognition threshold and noise level when the test symbol and background noise are in the same perceptual dimension, and (b) a constant recognition threshold when in different dimensions. The first hypothesis was confirmed for each color dimension, the second however, was only confirmed for background noise in L*. The L*, C*, h recognition thresholds increase with increasing background noise in C* or h. On the basis of some 16,200 visual observations we conclude that the three perceptual dimensions L*, C*, and h require different scaling factors (hue dependent for C* and h) in the CIE94 color difference formula, to predict detection threshold data for color noise. In addition these dimensions are not independent for symbol recognition in color noise. © 2008 Wiley Periodicals, Inc.