flash head has a power rating in watts, and while the compact
studio flash heads have the capacitor built in to the head,
there are larger units which have several flash heads
flash head can be driven from one large power unit where the
capacitors are stored . Most of these units have a dial that
allows the photographer to select over several power setting
for the particular needs of the shot. Some units do this with
a variable control that allows a flash intensity to be used
any where on the scale from the lowest setting to full power.
Other units do this with a step system only allowing perhaps
1/4, 1/2, and full power. In the adjacent diagram, you will
notice that the power settings range from 1/8, 1/4, 1/2, 1/1.
Each of these steps is one stop which is equivalent to one
stop on the aperture of the camera, one
stop on the shutter speed and also one
stop in terms of the films asa.