A monolight is a self-contained photographic flash lighting unit[1] typically found in studios. Bowens introduced the first in 1963. Each monolight has its own independent power source.[2] It does not depend on a centralized power supply as a "pack and head" system does. Monolights are also independently controlled: each has its own power settings and light output.[3] Flash power is predominantly measured by the industry in watt seconds, which is unit-equivalent to the joule.