Wiktionary
n. the lamp in a darkroom
Wikipedia
A safelight is a light source suitable for use in a photographic darkroom. It provides illumination only from parts of the visible spectrum to which the photographic material in use is nearly, or completely, insensitive.
Safelight is a 2015 American drama film, written and directed by Tony Aloupis, and starring Juno Temple, Evan Peters, Kevin Alejandro, Jason Beghe, Ariel Winter, and Christine Lahti. The film had its world premiere on April 17, 2015 at the Nashville Film Festival.
The film was released in a limited release and through video on demand on July 17, 2015 by ARC Entertainment.
Usage examples of "safelight".
Of course no one lit open flames on a ship, but the safelights set on medium flicker were lovely enough.
After that, I worked in the dull red glow of the safelights, squinting my way through the process slowly.
Peter turned out the amber light, then turned on the safelight, a small, glowing, red bulb which would not expose the printing paper.