Glossary of Terms

Open flash – a method of using any number of flash discharges to increase accumulated flash output over a period of time. The camera's shutter must remain open for an extended period of time, and the  method can therefore be used only when shutter speed is unimportant because of low ambient light levels.

Orthochromatic – a generic term for monochrome emulsions insensitive to red light. Monochrome printing papers are normally also orthochromatic.