The Pulfrich Effect: Lit & Finn (1976)

Newton 1726, p. 59:  Construction to compute the trajectory of a body released from an elliptical orbit. Lit, A. and Finn, J. P. Variability of depth-discrimination thresholds as a function of observation distance. Journal of the Optical Society of America, 1976, 66(7), 740 - 742.

Copyright (c) 1976, The Optical Society of America. Permission to copy the original paper, other than fair use, must be obtained from the author and the publisher.
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by John Michael Williams, 1999. Placed in public domain.

Some past studies have seemed to show that stereoacuity becomes poorer as observation distance is decreased from one meter, and that single-cell receptive field size in the visual system is not the reason for it. The geometric theory of stereopsis does not predict such a decrease.

This JOSA Letter reports unpublished, reanalyzed control data from the Lit and Hyman (1951) Pulfrich Effect experiment. The variance of settings was used as a measure of stereoacuity for fixed and moving targets with no Pulfrich filter in place.

One of the observers showed a mild degradation in stereoacuity with decreasing distance, both for fixed and moving (19 degrees visual angle per second) targets; the other observer showed no consistent change.

Reanalysis of available old data has left the problem unsolved. The literature of stereoacuity as a function of observation distance remains at best equivocal, and if there is an effect of decreased stereoacuity with decreased observation distance, it must be small or perhaps observer-specific.

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The Pulfrich Effect, SIU-C. Last updated 2000-07-23