Measuring Image Attributes in Units of Just Noticeable Differences for Natural Content

摘要

The four most important attributes from a consumer's point of view, namely brightness, contrast, color rendering and sharpness, are affected by four independent characteristics, being black level (BL), white level (WL), color saturation (CS) and contour rendering (CR). For the characteristics' impact on image quality they need to be expressed in a common unit, namely the just noticeable difference (JND). In previous research, the value of 1 JND for each attribute perceived in natural image content has been determined. To crosscheck these results the equality of the JNDs over the different attributes and the constancy of the JND over a larger range of change in the attribute need to be studied. This paper focuses on the constancy of the JNDs. It describes a subjective experiment in which participants are asked to choose the stimulus perceived exactly halfway of two images varied at different levels of each of the attributes. The results demonstrate that the JND remains approximately constant for each attribute in the range up to 4 JNDs.