Gray levels, dynamic range, contrast and DQE in imaging detectors

A very important parameter which characterises an imaging detector is the maximum number (Gmax) of luminance levels, or gray levels, that it can discriminate. In this paper a physical model is proposed regarding the possibility of determining Gmax by computing the detectable minimum signal difference (the gray step) in various experimental conditions. As a consequence it is demonstrated that Gmax is different from the dynamic range of the detector. The possibility of determining the minimum perceptible contrast (MPC) and the equivalence of the performance analysis of an imaging detector in terms of gray scale, MPC and DQE are also demonstrated.