Peripheral contrast sensitivity for sine-wave gratings and single periods

The contrast sensitivity of the human eye has been measured as a function of eccentricity. The stimulus used was a sine-wave grating with a fixed height of 5° in a surround of luminance that equals the average stimulus luminance. The measurements were carried out with stimulus width as the independent variable. The "local" sensitivity for gratings was found to decrease monotonically with increasing eccentricity. It was further found that the sensitivity for wide gratings is mainly determined by that part which is only 2° wide, situated as close to the fovea as possible. The results are discussed in view of the possible existence of "tuning", i.e. of a maximal sensitivity outside the fovea. at an eccentricity determined by the spatial frequency.