Flash Exposure Compensation Tips

Flash exposure compensation (FEC) changes the output level, or power level, of the flash unit on your DSLR camera without changing the background's exposure level. If the power level of the flash is set properly, adjusting the flash output level affects only the subject’s brightness, not that of the background.

Shooting with the external flash attached to the camera often produces a washed-out image with too much light. That’s where exposure compensation can help: It allows you to adjust the power of the flash unit to complement the external light, rather than overpower it. Here are some tips for controlling your DSLR’s flash.

To make the subject brighter, increase the FEC to a positive number. To avoid reflections or highlights, change the FEC to a negative number. The output level depends on the camera, but usually, you can adjust this between +3.0 and -3.0, at 1/3 increments. A setting of 0.0 is a normal flash value.

Each 1/3 increment is called a stop. So, dialing down the flash a stop or two means -1/3 or -2/3 on the flash exposure compensation dial.

When photographers use exposure bracket compensation, they shoot several photos, adjusting the exposure by a stop each time. You can do the same thing with FEC. For example, you can shoot at +1 FEC, then adjust to +2/3, +1/3, 0, -1/3, -2/3, and -1. This type of bracketing when shooting the same scene gives you a better chance of achieving the correct FEC.

As you take some flash photos, look at them closely on the DSLR’s LCD screen. Are you losing details in parts of the image, especially with the subject? Does the subject appear to be washed out, meaning that it approaches being all white? If so, dial down the FEC to a negative number. Viewing the photo's histogram also can help you determine whether the exposure is correct.

On most DSLR cameras, you set the FEC by pressing the flash button. Some DSLR cameras contain an FEC button instead, denoted in the menu by a flash icon with a plus sign and a minus sign. After selecting the icon, use the horizontal arrow buttons to adjust the setting.

A similar button with a +/- sign and no lightning bolt is the camera exposure setting button, which doesn't control the flash. Make sure you're looking at the correct number.

With some DSLR cameras, you can't set FEC when the camera is in automatic mode. You have to shift to program mode or manual mode, or a type of shutter or aperture priority shooting mode.

If you’re having difficulty controlling the external flash unit, make sure that the flash is fully compatible with your camera. Not all DSLR cameras can use all the features on all third-party flash units.

Any changes you make to the FEC setting might remain in place until you change the setting again, even if you turn off the camera. So, if you’ve made some odd changes to the flash settings to shoot a particular subject, you might want to change the settings back to a normal level before shutting down your DSLR.