Spatial nonlinearities of gray-scale CRT pixels

We measured the overall luminance, the luminance profile of individual pixels, and the interactions among neighboring pixels of a grayscale (i.e., non-color) CRT, using a two- dimensional CCD camera. We find that the luminance of a pixel depends on the luminance of the two preceding pixels in the raster, and that the interaction results in superadditivity. Furthermore, the luminance of a pixel depends on the proportion of the screen illuminated. Two consequences of these nonlinearities are that average luminance (as in a halftone image) cannot be predicted from the linear summation of individual pixel spread functions, and that inverting the polarity of a display does not simply invert the luminance profiles. These interactions must be taken into account wherever the luminance profile of displayed stimuli is important.