Research on spatial distribution of brightness perception: The optimal experimental sampling parameters

The study was a previous research for spatial distribution characteristics of the spectral luminous efficiency function in the whole field of vision. Psychophysical experiments were conducted to investigate the spatial distribution of brightness perception and the optimal experimental sampling parameters by direct brightness-matching method. Two visual stimuli, a central fixation point and a peripheral target, were presented in different combinations of shape, color, luminance, diameter and spatial position, to explore the sensitivity of human eyes. The compared target was gradually moved away from the position adjacent to the fixation point. After moving of every sampling step, subjects responded whether the brightness of two stimuli were the same. Statistical analyses showed the conclusions as follows. (1) Blue was the most sensitive color to eyes, under the condition that diameters and directions of the stimuli were the same. (2) Under the condition that colors and directions were the same, the smaller diameter caused the more sensitive perception. (3) The visual perception of the human eye had spacial distribution characteristics: the left visual field was more sensitive than the superior field; the inferior field was more sensitive than the superior field; and under partially parametrical conditions the left field was more sensitive than the inferior field. These discrepancies of the brightness sensitivity in space domain could be explained by the heterogeneous photoreceptor distribution. Finally, we obtained the optimal combination of parametrical levels of stimuli for the spatial sampling of the brightness perception: blue color, diameter of 0.5° visual angle.