Abstract: A highlight mask, especially suited for printing from positive color transparencies, is made of photochromic glass which, like Corning PHOTOGRAY EXTRA sunglass lens material, darkens not only under ultraviolet radiation but also under visible radiation in the blue range. The mask is made by mounting, onto its upper surface, a photo transparency and exposing it to flashes of intense light strong in the blue range. Such radiation penetrates the thin or highlight areas of a photo transparency, regardless of their color tint, and creates a negtive highlight-masking image in the glass. While it does not effect general contrast reduction over the entire film area, the highlight masking image requires no further development, remains in registration with the transparency for photoprinting, and fades in time or when heated, so that the glass may be reused.