panel which every member is experienced grader of beef quality was established to evaluate algorithm
performance. Their vision thresholds were firstly determined. When testing, every panelist defined a critical interval of grey level in each test card in accordance with following categories: the examinee’s attitude gradually changes from “Uncertainty” into “Certainty” when they think they observe a comparatively brighter diamond light spot on a comparatively darker background. Additionally, all diamond light spots before the critical interval cannot be observed but all spots behind it can
be clearly observed.