The effect of target line length on Vernier acuity in white and blue light.

Abstract Experiments are described in which Vernier acuity performance is measured for four subjects using four different target line lengths. The results show that target line length is a significant factor in the achievement of the small thresholds of Vernier acuity. They are consistent with a process of spatial summation of information regarding the relative location of the target lines upon the retina. A correlation is shown between the information transmitted by the visual system per setting and the logarithm of target line length. The results are compared with a simple model of homogeneously distributed spatially quantised receptors.