The size of the pupil has a large effect on visual function, and pupil size depends mainly on the adapting luminance, modulated by other factors. Over the last century, a number of formulas have been proposed to describe this dependence. Here we review seven published formulas and develop a new unified formula that incorporates the effects of luminance, size of the adapting field, age of the observer, and whether one or both eyes are adapted. We provide interactive demonstrations and software implementations of the unified formula.
1 I am indebted to Robert Ollman, especially for pointing out to me that Eq. 6, which is valid for the special case rri = rra = .5, holds more generally for any presentation probabilities in the form of Eq. 3. I thank also
Abstract-Todetermine whether the spatial disorder of human photoreceptors is sufficient to prevent aliasing distortion.optical transform techniques were used to compute the power spectrum of a 12' x 13' array of fovea1 cones treated as sampling points and also the post-sampling spectra of gratings at spatial frequencies above (80 c/deg) and below (30 c/deg) the nominal Nyquist frequency for this array.No trace of aliasing was observed in the spectrum of the sampled 80c/deg grating. The conclusion is that spatial disorder in fovea1 receptor placement allows alias-free sampling without introducing any appreciable spatial noise.
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