Confidence rating based calibration and resolution indices were obtained in two experiments requiring perceptual comparisons and in a third with visual gap detection. Four important results were obtained. First, as in the general knowledge domain, subjects were underconfident when judgments were easy and overconfident when they were difficult. Second, paralleling the clear dependence of calibration on decisional difficulty, resolution decreased with increases in decision difficulty arising either from decreases in discriminability or from increasing demands for speed at the expense of accuracy. Third, providing trial-by-trial response feedback on difficult tasks improved resolution but had no effect on calibration. Fourth, subjects can accurately report subjective errors (i.e., trials in which they have indicated that they made an error) with their confidence ratings. It is also shown that the properties of decision time, conditionalized on confidence category, impose a rigorous set of constraints on theories of confidence calibration.