Abstract

In the measurement of contrast thresholds for stationary, stabilized images, the choice of the psychophysical procedure may profoundly affect the results by constraining the time course of the stimulus presentation. With some procedures, the subject is unable to ignore transients; as a result, he necessarily responds to onset and offset transients rather than to the intended stimulus. Here we report significant effects of (a) the rapidity of onset and (b) the duration of the stimulus on thresholds for stabilized sinusoidal-grating patterns; these effects occur with both forced-choice and standard yes/no procedures. No value of either parameter (a) or (b) can eliminate such presentation effects when these procedures are used. However, we have devised a new, continuous-presentation procedure that yields results that do not depend on these parameters. Contrast thresholds for stabilized and for unstabilized stimuli measured by this procedure differ by 1 log unit or more, in good agreement with the results obtained by careful use of the method of adjustment.

© 1982 Optical Society of America

Motion and vision. IV. Isotropic and anisotropic spatial responses

D. H. Kelly
J. Opt. Soc. Am. 72(4) 432-439 (1982)

Contrast sensitivity measures and accuracy of image stabilization systems

Ülker Tulunay-Keesey and Robert Michael Jones
J. Opt. Soc. Am. 70(11) 1306-1310 (1980)

Thresholds at luminance edges under stabilized viewing conditions

Francis X. J. Lukas, Ülker Tulunay-Keesey, and John O. Limb
J. Opt. Soc. Am. 70(4) 418-422 (1980)

Fading of stabilized retinal images

Ülker Tulunay-Keesey
J. Opt. Soc. Am. 72(4) 440-447 (1982)

Contrast thresholds with stabilized and unstabilized targets

Ulker Tulunay-Keesey
J. Opt. Soc. Am. 72(9) 1284-1286 (1982)