Watts per second

WS ( Watts per second)
For flash mode, the measurement of electrical energy in the flash.
WS
Watt per second. For flash mode, the measurement of electrical energy in the flash ...

These flash systems are generally much more powerful than compact flashes and their output is measured not by a guide number but by watts per second (Ws). Models over 400 Ws mostly have to be powered by an external power source.

See also: Softbox, Space, Memory, Synchronization, Coated