Definition of orthochromatic in US English:



  • (of black-and-white photographic film) sensitive to all visible light except red. Orthochromatic film can therefore be handled in red light in the darkroom but does not produce black-and-white tones that correspond very closely to the colors seen by the eye.

    Often contrasted with panchromatic
    • ‘I use traditional panchromatic films for the interpositive and an orthochromatic film for the final enlarged negative.’
    • ‘Orthochromatic film was only sensitive to the brightest natural light.’
    • ‘Even the orthochromatic films were not sensitive to red light.’
    • ‘As plates and films became more sensitive (orthochromatic emulsions are sensitive to green as well as blue light), ruby safelight filters became necessary, but the old manipulation techniques could still be utilized.’
    • ‘Orthochromatic photography refers to an emulsion that is sensitive to only blue and green light, and thus can be processed with a red safelight.’