Abstract

Vernier acuity is less degraded by blur than is resolution acuity. However, unlike resolution, the amount of degradation of vernier acuity depends on the contrast of the stimulus and the type of blur. We used both two-dimensional, and one-dimensional Gaussian blur. The following results were found. At low contrast, vernier acuity has a weak dependence on the type of blur and begins to be degraded at blur standard deviations as low as 1 min. At high contrast the degradation does not occur until 23 min, and in the two-dimensional case the falloff of vernier acuity with blur becomes quite steep with an exponent of 1.5. We explored the shapes of the threshold-versus-blur curves for three different strategies of fixing contrast: (1) fix the peak contrast independent of blur, (2) fix the "energy" (%min) so that the peak contrast is inversely proportional to blur, and (3) fix contrast in threshold units so that contrast increases with blur. Each of these procedures is appropriate to different situations, and each leads to different notions about how vernier acuity depends upon blur.

© 1990 Optical Society of America