adj.PhotographySensitive to blue and green light.


Orthochromatic describes the spectral sensitivity of monochromatic (black-and-white) photographic materials, which are not sensitive to red light. As a result, reds and oranges in the original appear much darker relative to blues and greens of equal brightness. Early photographic materials, especially film and plates used in the camera, were orthochromatic. Most black-and-white photographic papers continue to use orthochromatic emulsions, allowing the materials to be handled in the darkroom under red light.