Exposure Compensation

Exposure compensation is what you can do to override the exposure settings set by the camera's metering system.

The metering system in your camera measures the amount of light in the photo and tells you the aperture and shutter speed needed for a correct exposure.

The examples below show the various results of using different exposure compensation settings.

Multi-Segment Metering
Most cameras use multi-segment metering as the default metering system. This metering system measures the brightness in several areas in the photo and finds an average (emphasis varies depending on the camera). This type of metering can be fooled by more challenging lighting conditions such as strong backlighting.

Strong backlighting conditions are where the amount of light on the background is far more intense than the amount of light on the foreground area. This usually happens when you shoot a subject indoors, with a brightly lit outdoor background.

Ideal lighting conditions are where there is a similar amount of light illuminating both the background and foreground. Ideal lighting is where the camera's multi-segment metering does a good job.

Spot Metering
For pinpoint control on the area for which the camera measures brightness, use spot metering if it's available. This metering system only samples a point within the photo (usually in the center) instead of several areas. You can press the shutter release halfway to meter the desired area, and then re-frame the shot.

Alternatively, take an exposure reading with spot metering, note the aperture and shutter speed, and switch to manual exposure mode. This enables you to focus on a subject which isn't what you measured the exposure on.