The Pulfrich Effect: Lythgoe (1938)

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Synopsis (no author abstract)

This was one of the few preWWII studies of the Pulfrich effect. The results are reported informally, as an "executive summary" for medical doctors.

Although he refers consistently to illuminance rather than luminance, Lythgoe does not describe his apparatus, so it appears that his results may not have taken variations of the natural pupil into account. Lythgoe's fit to his data led him to postulate an empirical equation for the Pulfrich latency difference equivalent to,

with I_U the upper (higher) level of illuminance. The formula seems meant to refer to photopic levels of illumination, only.

Lythgoe attempted to isolate the effects of target vs background as well as that of stray light, with mixed success. He reported a decline of the effect with time in dark adaptation, a result not confirmed in later studies. Systematic control for pupil size and point of fixation would have to await the work of Lit.

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