The RaPID Perceptual Image Description Method (RaPID)

This paper contains a general description of the RaPID (rapid perceptual image description) method, and the results of a series of experiments on the attribute sharpness. The method aims at a rapid and perceptually meaningful description and quantification of the primary factors of image quality. The purpose of the project is primarily to develop the main dimensions of image quality, but also to determine how they combine into overall image quality, and to develop perceptual models for the main dimensions. The result of the project will be a technique that can be used to evoke, quantify, analyze and interpret subjective reactions to the characteristics of imaging systems. A preliminary experiment was conducted on sharpness related attributes of images. The results showed that the five TV sets under study had to be evaluated on 11 different terms and that they combine into two independent attribute dimensions for natural or test images. If both types of images are considered simultaneously, the 'sharpness' space consists of at least 3 dimensions. Physical measurements were used to calculate sharpness related measures (MTFs, step responses, line width) and these were correlated with the subjective results.