Do you use your built in flash or an add on flash unit and get frustrated when your images are too bright or too dark?
Chances are you’re using flash in a fully automatic mode and the calculations made by the camera/flash unit are resulting in too much or little light being emitted by the flash. Just like exposure compensation (see recent post), where you can adjust the cameras automatic exposure calculations by forcing the camera to over or under expose a little, you have the same control over the power of your flash.
Most DSLR cameras with a built in flash will allow you, either via the menus or via the quick controls on the rear of the camera, to turn the flash power up or down. Depending on your camera, you may be able to apply whole stops, half stops or thirds of a stop. (One full stop equals a doubling or halving of the power of the flash, i.e. +1 or -1 stop.)
For example, if you’re taking a portrait, and the flash is too harsh, i.e. too powerful, you might apply a flash exposure compensation (FEC) or -1 stop. For an image that’s too dark, maybe +1, or more stops will be necessary. Remember though, you can’t go beyond the capabilities of the camera/flash – e.g. if the flash is already firing at full power, then you can’t add another stop!
Check your camera and/or flash manual for more on flash exposure compensation.