When to Use Exposure Compensation

Exposure compensation is the deliberate lightening or darkening of a photograph. Most DSLRs can adjust a photo's exposure within the range of -2EV to +2EV. For example, if you set the camera's exposure compensation to -1EV then you, in effect, are underexposing the shot by 1 stop and vice versa. Depending on your camera, you can set the exposure value (EV) by 1/2 or 1/3 increments.

The Purpose of Exposure Compensation
Most of the time, when you take a picture and the subject is predominantly bright, the camera will tend to underexpose it. The reason for this is that the camera will try to make whatever subject it meters, whether it's predominantly bright or dark, a middle shade of gray. To do this, the camera will make the scene either too dark if the subject is bright or too light if the subject is dark.

This is where exposure compensation comes in. Let's say you are taking a tightly cropped photo of a bride and her wedding dress. Since the photo will be predominantly bright with the bride's white dress, the end result will be a photo that is slightly underexposed. In order for you to properly show the bride's dress to be white, you will need to set your exposure compensation to overexpose by selecting a positive EV. It's also the same when taking photos of subjects that are primarily dark colored. The camera will be fooled into making the whole scene lighter so a negative EV will have to be added to render the scene more accurately.

The photo below was taken in RAW format so the EV could be changed during post processing. During the shoot, the little girl's face was the area where the camera metered the exposure. Since she has fair skin, the camera rendered it a little darker than it actually was.



This was the result when an exposure compensation of +1 was added. The tone of the skin was rendered more accurately by overexposing the photo.



There is no exact science of how much exposure compensation to use for any particular scene. It will always depend on the quality of light and of course, personal preference. Just check your camera's histogram to make sure that you're not blowing the highlights or making everything too dark when modifying a scene's exposure.