Each time you take a flash photograph, you make two exposures at the same time. You're making an exposure of the ambient light, and an exposure of the flash's light. Whether you take this into account or not, it is happening every time. The ambient exposure is controlled by the f/stop and the shutter speed.   The exposure of the flash's light is controlled only by the aperture and the flash power.  The aperture controls how much light is let through the barrel of the lens and the flash power controls how much light is coming.  Think about it, your flash fully discharge in 1/10,000 sec... at least the Paul C. Buff Einstein I use does.  That means the light is fully discharged regardless of the shutter speed.  Mixing ambient and flash to get a single, pleasing exposure is surprising easy when you learn a few, simple rules, tricks, and tips.

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