The Pentax flash control system lets you set a flash compensation value on the camera body which is cumulative with any value set on the flash itself. Having two independent settings is most important when using multiple flashes for a scene, but it also gives increased flexibility, since it adds a couple of stops to the range and because many Pentax camera bodies can work in ⅓-stop increments.
With the exception of the AF200FG (which only offers Auto, -0.5, or -1), the Pentax and Sigma flashes allow compensation from -3 to +1 in half-stop increments.
The Metz flashes allow EV -3 to EV +3 in third-stop increments, except for the 36 AF-4, which has no independent compensation control.
The Promaster and Sakar flashes don't have separate on-flash settings (but are still affected by the camera's setting for flash EV compensation.)
