Patent US 4,991,007

A system and method for evaluating a visual image characteristic, such as the brightness, color, tonal scale, geometric linearity, sharpness and/or position, of an electronic image signal, such as obtained, for example, from a television camera. The image signals, including an image of a test target, pass to an image combiner. A reference image signal from a reference signal generator also passes to the image combiner and a combined signal then passes to a monitor on which the image of the test target and the reference image are displayed in juxtaposition for comparison. An adjustable image signal modifier adapted to modify the desired signal characteristic can be provided between the camera and the combiner. An operator then adjusts the image signal modifier until the selected characteristic of the two images as displayed have a predetermined relationship. The extent of such modification can also provide a quantification of the deviation of the image of the test target from a predetermined relationship with the reference image for the selected characteristic. Further image signals appropriately modified as obtained from the image signal modifier can be transmitted or recorded for later dissemination. Quantification of the deviation can also be obtained by recording the required modification of the reference image signal.