Exposure compensation is a functionality provided by most digital cameras, even by the cameras on smartphones. It allows you to overpower the camera’s exposure settings and make the photos look brighter or darker. Why would you want to do this when your camera is perfectly capable of evaluating the lighting of a scene and setting the right exposure? Well, because the camera isn’t always right. Or because you might have a more creative approach than your camera.
Digital cameras have a built-in exposure metering system that evaluates the intensity of the light and decides what parameters to use. If you set the camera on Auto mode, it will set both aperture and shutter speed to match the lighting conditions and provide the correct exposure. But if you set the camera on Aperture Priority or Shutter Speed Priority modes, it will select only the shutter speed or, respectively, the aperture. However, there are situations in which the camera fails to correctly assess the intensity of the light.
How the exposure metering system works
Digital cameras provide three metering modes: spot metering (the camera evaluates the amount of light around the focus point), center-weighted metering (the camera evaluates the amount of light around the middle of the frame), and matrix metering (the camera divides the frame into zones and evaluates the amount of light based on those, giving higher importance to the zone where the focus point is).
While most manufacturers use these three metering modes, they may have different algorithms for determining the final settings. To help the system have good results, you have to change the metering mode according to your scene and preferences. For example, you may have better results for a portrait if you choose the center-weighted metering mode. For landscapes, you usually want the matrix mode. The spot metering mode works best for singular subjects that aren’t in the center of the frame, such as birds, wildlife, or the moon.
When you need exposure compensation
You usually need exposure compensation when the scene has an extremely bright or dark area you want to correctly expose. In these situations, the built-in metering system may fail because it either tries to average the amount of light from a larger area or exposes correctly for the chosen area but over/underexpose the rest of the frame. To make an idea, think of the spot of light used at concerts, shows, and plays. If you want to have both the subject and the background correctly exposed, you need exposure compensation.
Another situation that requires exposure compensation is a white snowy landscape or a sunny day in the desert (the camera will underexpose everything that isn’t covered in snow or sand), or a dark forest (the camera will overexpose the patches of sky seen through the branches). The camera assumes that the scene has the entire range of brightness and when the scene is very dark or bright the camera can’t work out the right exposure.
You may also want to create artistic low-key or high-key photos and intentionally underexpose or overexpose the frame. Why not? A photographer should forget about rules from time to time.
How to use exposure compensation
Set the camera in one of the semi-automatic modes (Aperture Priority, Shutter Speed Priority, and Program). Only these modes will give you access to exposure compensation settings. Then access the exposure compensation settings and evaluate if the photos need to be brighter or darker.
The (+) sign increases the exposure while the (-) character decreases it. Exposure compensation is measured in stops, and most manufacturers offer intermediary steps such as 1/2 and 1/3. A full stop will double or halve the current exposure.
Based on the camera mode you chose, exposure compensation will change a parameter to allow more or less light into the camera. In the Aperture Priority and Program, the camera will adjust the shutter speed. While in the Shutter Speed Priority, the camera will change the aperture.
And that’s it! As you can see on the camera’s screen, the result of exposure compensation adjustments. You can explore the range of possibilities and decide what goes best for your composition.