Fixed focus is a lens camera system that has no method of focusing on a fixed point, usually at the hyperfocal distance. Fixer is a chemical solution used for fixation. Flare is a non-image forming light scattered by the lens or reflected from the camera interior. Flash is an artificial light source giving brief but very bright illumination. It is produced by a combination of certain gases within a transparent tube.
Flash bulb is a replaceable bulb for use in expendable flash units.
A glass bulb contains a pyrotechnic wire or paste which burns out in a brilliant flash when a low voltage firing current is applied. Flash cube is a now obsolete bulb containing four small flash bulbs built into a single unit. Flash factor is a number which provides a guide to correct exposure when using flash. See also Guide number . Flashing is briefly and evenly exposing photographic materials to white light.