2. For each eye and pupil diameter we then computed from the Zernike coefficients the discrete OTF for polychromatic (equal energy spectrum) white light, using the methods described in Watson and Ahumada (2008, 2012) and based on methods of Ravikumar et al. (2008). Zernike radial orders of two or greater were used. We used a center wavelength of 555 nm and a wavelength spacing of 20 nm, weighted by luminance. The discrete OTF was 256 · 256 in size. The scale of the discrete OTF and PSF depends upon pupil diameter. Pupil diameters from 2 to 6 mm yield PSF image resolutions of 521 to 174 samples/deg and OTF resolutions of 2.035 to 0.678 samples/cycle/deg, respectively.