Some studies on judgment and decision-making have demonstrated that uncertainty in probability influenced curvature of function given by judged probability or proportion (i.e., probability weighting function). In this study, we concentrated on proportion judgment about visual input. We investigated the possibility that the efficiency of feature detection of visual stimuli would be related to uncertainty in their proportion judgment. Concretely, our participants in the experiments performed proportion judgment task using two sets of visual stimuli pairs, "red vs. green dots" and "right vs. left tilted lines". In addition, we adopted different types of responses; in one condition, the participants were asked to response using numerals; in another condition, they were asked to response by adjusting the line bar which indicated the proportion. Our results suggested that the efficiency of feature detection of visual stimuli influenced the curvatures of the probability weighting function.