The proposed standard defines a gray-scale display function for monochrome image presentation devices, such as cathode-ray-tube (CRT) monitor/display-controller systems and digital laser image printers. The display function is based on perceptual linearization. It is defined for the luminance range of 0.05 to 4000 cd/m2. The standard provides a mathematical formula for the standard display function as well as a table of the luminance levels of the just-noticeable differences (JNDs) of a standard target. The standard facilitates similarity in gray-scale between different image display devices independent of their luminance. The standard does not eliminate the use of application-specific display functions, but rather assures their effectiveness through the standard display function. To realize conformance of an image presentation device with the display function standard, standard test patterns are defined. The patterns are used to measure the luminance of the display or optical density of a print as a function of digital input. By proper interpolation of the inverted measured characteristic function of the display system and inserting the desired standard luminance values for every digital input, a transformation can be computed so that the display system may conform with the display function standard. The standard also defines the dynamic range of an image presentation device as the number of JNDs that theoretically can be realized for a given digitization resolution and the standard target. Interpolation processes and potential conformance measures for the standard are discussed. The proposed display function standard is essential for the proper realization of image presentation services according to the DICOM Standard. The relation of the standard display function to DICOM-defined look-up tables is outlined.