Quantum efficiency of human vision.

The detective quantum efficiency for foveal vision is computed from the flash perception data of Blackwell and McCready. The detective quantum efficiency is identical with the concept of quantum efficiency introduced by Rose in 1946, and is defined as the square of the ratio of the smallest possible threshold to the observed threshold, where the smallest possible threshold is set by the statistical fluctuations in the number of the background photons entering the eye. The computed values of the detective quantum efficiency Q are tabulated in Table V, and depend on the target diameter α, on the light pulse duration T, and on the background luminance B. The maximum values of Q (with the respect to variation of α and T) range from about 0.25% to about 1.0 %over the range from 0.1 to 100 ft-L, with the maximum value occurring at about 1.0 ft-L. The computed values of Q are free of the questionable assumptions previously used by Rose and by Jones regarding integration time and threshold signal-to-noise ratio.