1924 First C. I. E. photopic luminosity function. 1925 Holm demonstrates that vitamin A deficiency causes night blindness. Stiles and Crawford demonstrate directional sensitivity of cones. Wald finds vitamin A in rhodopsin. LeGrand measures visual acuity bypassing the optics of the eye.
Stiles introduces Pi mechanism analysis of increment thresholds.
1942 Hecht, Schlarr, and Pirenne show that rods respond to single quanta. 1943 DeVries-Rose law. 1947 Granit distinguishes sustained and transient ganglion cells. Gabor describes principles of holography. 1951 C. I. E. standardises scotopic luminosity function.