safelight
/ˈseɪfˌlaɪt/
noun
- A special lamp used in a darkroom that produces light of a color and intensity that does not damage photographic film or paper.
- Make sure the safelight is the correct type for the film you are using.
- The photographer turned on the safelight before developing the film.
- Under the dim red glow of the safelight, she carefully placed the paper in the developer.