WILLIAMSMTF Compute the MTF measured by Williams et. al.
mtf = WILLIAMSMTF(s)
Compute the MTF measured by Williams et. al. for 633 nm light,
representing the optical quality of human foveal vision. The empirical
MTFs were obtained for a 3 mm pupil.
Williams, D.R. Brainard, D.H., McMahon, M., and Navarro, R. (1994).
Double pass and interferometric measures of the optical quality of the
human eye. Journal of the Optical Society of America A, 11, 3123-3135.
Formulae given in Equation 1 ff.
Spatial frequency passed in cycles/deg.
See also OTFTOPSF, WILLIAMSRESTMTF, DIFFRACTIONMTF,