The relationship between image fidelity and image quality

Image fidelity (inferred by the ability to discriminate between two images) and image quality (inferred by the preference for one image over another) are often assumed to be directly related. We investigated the relationship between the perceived image fidelity and image quality of halftone textures. Subjects were asked to rank order a set of printed halftone swatches on the basis of smoothness. They were then asked to reduce the contrast of each pattern until it was at threshold, thus providing an estimate of the pattern's perceptual strength and its discriminability from a non-textured swatch. We found only a moderate correlation between image fidelity and image quality.