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Exposure Compensation: How It Works And When To Use It

Three keys to understanding how this camera setting affects exposure and how to put it to use

One of the unsung heroes of camera controls is exposure compensation. Sure, those fancy automatic exposure modes get all the press, and manual mode has the street cred. But exposure compensation is like the best of both worlds!

The exposure compensation dial (or adjustable menu setting) allows you to influence the way the camera determines a correct exposure. It’s like your direct line to tell your camera, “Hey, whatever you think the correct exposure should be, I’d prefer it if you over- or under-exposed from there.

I only use exposure compensation when I’m in an automatic exposure mode. In manual mode, the photographer dials in exactly what the exposure settings should be—the shutter speed, the ƒ-stop and the ISO. But in an automatic exposure mode—whether that’s the auto ISO setting, shutter- or aperture priority, or full program mode—the photographer is deferring to the camera’s TTL metering to automatically set the exposure. Because the mode you choose determines what settings will be fixed and what the camera can change, exposure compensation changes different settings in different modes. 

In aperture-priority, for instance, if I’ve dialed in the aperture of ƒ/8 and the camera chooses a shutter speed to accompany it, by setting the exposure compensation to +1, I’m directing the camera to overexpose by one stop. Because I’m in aperture priority mode, the result is that the camera will slow down the shutter speed in order to overexpose. (In shutter priority, I set the shutter speed and the camera will change the aperture, and in a manual exposure mode with auto ISO set, the aperture and shutter speed will stay fixed while the exposure compensation is done by automatically adjusting the ISO.)

There are two primary scenarios where I rely on exposure compensation to get more accurate exposures: When the subject of my photograph is strongly backlit or when the scene I’m photographing is predominantly composed of very dark or very light tones.

First, let’s look at backlighting. We’ve all, no doubt, aimed our cameras at a friend or family member seated in front of a window and made a beautiful… silhouette? That happens because the camera sees all that bright outdoor light surrounding the subject and thinks that it’s what you’re trying to expose for. Consequently, it chooses an exposure appropriate for an outdoor lighting scenario. And when that happens, the person sitting indoors in front of that bright outdoor illumination is left in shadow. Cameras quite simply get fooled by backlight. It’s in this scenario that I most often use exposure compensation and will use it to the extreme.

My camera’s exposure compensation dial goes to plus and minus three full stops of exposure compensation, and in a strong backlit situation, overexposing by two to three stops is easily required if you have any hope of seeing the details in your subject’s backlit face. The only downside of using exposure compensation in this kind of scenario is that while the subject’s face might be more readable, that bright background is going to be wildly blown out. It’s for this reason that exposure compensation is the lesser of two evils. A more ideal solution might include adding a reflector, a flash fill or even changing the positioning so that the subject is not backlit. But when the situation forces your hand and you need to get a readable exposure in backlighting, exposure compensation shines. 

The other scenario in which I regularly employ exposure compensation is when I’m looking at a scene that’s comprised largely of dark tones or light tones. For years, I’ve referred to the examples of a black cat wearing a black hat in a black room or a white cat wearing a white hat in a white room. If I’m completely honest, however, I must confess that I’ve yet to actually encounter those two scenarios in real life. What I do encounter, though, is a person with dark skin wearing a dark suit photographed against a dark background. Or a person with light skin wearing a light dress photographed against a light background.

Both of these scenarios deliver exactly that “white cat/black cat” scenario and confuse our cameras because of the preponderance of light or dark tones. These situations are known as high-key (bright) and low-key (dark) and they inevitably lead to incorrect exposures. The reason? Because no matter how advanced their TTL metering and internal processors become, our cameras are fundamentally still aiming for a “middle” tonality when determining exposure. They simply don’t expect all dark or all light tones in a scene.  

I find that if I think of my camera as aiming for middle gray with every exposure, the need for exposure compensation becomes much clearer. The black cat in the black hat in the black room will look overexposed due to the camera’s attempt to make it appear middle gray. Likewise, the white cat in a white hat in a white room will no doubt look underexposed by default. Sometimes, just a little adjustment from a half stop to a stop or more can be sufficient to account for such under- and over-exposure predilections. So, the next time you notice your scene is low light and filled with dark tones, expect that the camera will inevitably try to overexpose it and turn the exposure compensation dial to account for the issue and deliver a more accurate exposure.

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