Limiting Factors in Threshold and Suprathreshold Vision

摘要: THE threshold contrast of object detail decreases with increasing size; the full curve Fig. 1 shows circular details as a function their angular diameter1. To explain form this some2–4 have proposed that noise is less effective in “obscuring” larger details; others5,6 suggested loss optical and neural processes for details. This fundamental uncertainty has not yet been resolved7. According to first view, sampled over equivalent area detail. Because number (N) random events would be integrated area, relative standard deviation (N−½) less, fact inversely proportional diameter (Fig. 1, dotted line). second effect constant different diameters detail, results solely from variation loss. The arises imperfections processes. may quantitatively described terms transfer function. For present purpose, defined ratio subjective brightness objective luminance expressed diameter. Both contrasts refer centre relation its background.