Why red light is used in dark rooms for the development of photograph?
The darkroom does not have to be completely dark when making black and white prints. Most black and white print papers are only sensitive to blue light, or to blue and green light, so black and white darkrooms feature a specially-made red or amber coloured light, known as a safelight. It enables the photographer to work in the light so they can see what they are doing, without exposing the paper. A low-intensity orange or yellow light can also be used, but these are less common than the red safelight. Colour print paper, on the other hand, is sensitive to all parts of the visible spectrum and therefore must be kept in complete darkness until the prints are properly fixed. There is however a very dim amber safelight that can be used in colour photography, but its so dim as to be of little use. For both colour or black and white paper, a “paper-safe” — a light-proof box to safely store photographic paper not in use as opposed to the boxes and light-proof bags that the paper comes packag
