Contrast and visibility

The purpose of the present report is a study of literature related to analytical visual performance models and a discussion of various approaches with respect to a further development of a CIE contrast metric of visibility. It has been shown that many developments have taken place during the last 10 or 15 years which permit a much improved understanding of the multiparametric interactions in visual performance thresholds and in capability of predicting them. We have presented the concept of visibility lobes per glimpse which reveals a basis for evaluation of visual tasks and lighting conditions. An analytical function is discussed which includes foveal and extrafoveal vision, target-background interference, and information load. A critical point is the appropriate definition of contrast. It should be distinguished, for example, between inner and outer contrast. Furthermore, different filtering channels have to be taken into account if contrast sensitivity is measured. Contrast sensitiv ity as a function of spatial frequency must be determined for the prediction of detection and discrimination capabilities of observers. Priority of further work should be given to the investigation of visibility lobes as a function of target and background structures.