In the field of optical image evaluation, the knowledge of spatial frequency character (response function) of the human eye is very important, for it is the human eye that evaluate the image which is formed by photographic lens or seen on photographic film. In designing a telescope and binocular optical system, data on response function of the eye can be effectively used.
Response function of the eye is defined as B/ΔB. In this case B is the mean luminance of sine wave line pattern and ΔB is the amplitude of pattern at threshold contrast.
Measurement is made at three luminance levels: 600rlx, 200rlx, 40rlx. Sine wave line pattern is made out of density type sound positive film.
In this report, numerical values of spatial frequency are expressed in terms of line number per millimeter at the viewing distance of 250 millimeter. As the field luminance B is decreased, the gain of response function is reduced in high spatial frequency region, but the maximum value remains almost unchanged.
