An instrument developed for the U.S Air Force, the Variable Contrast Illuminator, permits continuous variation of the contrast and color of a bar target source. The target consists of transparent areas ruled through a reflecting substrate. The colors of the transparent areas, the reflecting areas, or an area superposed over both clear and reflecting areas may be independently varied. The color variations are formed by selective attenuation and synthesis of red, green, and blue light paths. The white light in tensities of transparent and reflecting areas may be independently varied to produce contrast ratios from over 1000:1 to 1:30, i.e. from bright areas on a dark surround to dark areas on a bright surround. Recently a company investigation has shown the feasibility of providing a ruled target with three bar patterns(√2 progression) extending from 3.2 lines per mm to 228 lines per mm.