Understanding Exposure Compensation

The exposure of a photograph is controlled by three variables using the camera: Shutter Speed, Aperture, and ISO. Using the Manual Mode is not the only approach to take control of the exposure values, you can do so using other non-automatic modes as well. This can be done using any digital camera by brands such as Canon, Nikon, Sony, etc.

Using aperture priority mode, shutter priority mode and program mode lets you get rid of the automatic mode, which is a step forward in understanding how the camera works. These modes allow you to adjust at least one variable which affects the exposure, thus giving you partial control over your camera but still retaining control of other variables with the camera.

You can over overrule the control of the camera and take control of all the variables by using exposure compensation. This will allow you to take charge of the exposure variable which was earlier being controlled by the camera. In short, by using the exposure compensation feature you can override the exposure reading that your camera suggests you. In this blog post, I am going to discuss the benefits, situations and ways of using exposure compensation.

Why should you use exposure compensation?

The light meter in a digital camera is engineered in such a way that it exposes every object for 18% gray (middle gray tone), irrespective of the object’s ability to reflect back the light. The camera’s meter can be mislead by varying light tones, thus resulting in overexposed or underexposed photos.

If you photograph anything which is brighter than 18% gray color tone (for example a white shirt), your camera meter will try to under exposure the white shirt because it is engineered to see everything as 18% gray, thus converting it into underexposed frame. Similarly, if you point your camera towards anything which is darker than 18% gray color tone (for example a black car), it will try and overexpose the frame because your camera is trying to see the shirt as 18% gray.

In order to counter such situations and to make the exposure correct, you should use the exposure compensation. It takes practice, but once you start using it you will get used to it.

When should you use exposure compensation?

Situation 1: As discussed above, if the average of light tones in your scene is brighter than mid-gray, the light meter will try to reduce the exposure in order to correctly expose the scene. Though the camera is trying to correctly expose as per 18% gray tone, you actually want to capture the actual tones exactly how you see from your eyes. In this procedure, the camera will produce an underexposed photo. So if you are photographing a white shirt, the camera meter will try to make it mid-gray and thus underexposing the photo.

To counter the exposure reading suggested by your camera, you will have to use the exposure compensation feature in order to increase the exposure manually. Using exposure compensation you will have to bring the pointer of the exposure meter (displayed on the screen at the back of the camera) towards ‘+’ in order to increase the exposure and get a photo with the light tones that you desire.

Situation 2: If the average of light tones in your scene is darker than mid-gray (18% gray tone), the camera’s light meter will increase the exposure to correctly expose the scene as per 18% gray tone. In this practice, the camera will capture an overexposed photo. So if you are clicking a black shirt, the camera meter will try to make it appear as mid-gray and thus overexposing the photo.

In order to override the exposure reading suggested by the camera, you will have to reduce the exposure manually by using exposure compensation. With the use of exposure compensation you can reduce the exposure to get desired light tones, all you have to do is move the pointer of the exposure meter towards ‘-‘.

Situation 3: There is no hard and fast rule that you always have to capture ‘correctly exposed’ photo, being an artist and a creative mind you are free to experiment anything. Sometimes you might want to capture a dramatic portrait, which can be achieved by adjusting the exposure meter towards ‘-‘ using exposure compensation. Similarly, you can capture dreamy portrait by adjusting the exposure meter towards ‘+’.

How to use exposure compensation?

There is a button on your digital camera with a ‘+/-‘ icon printed on it (as shown in the image below), pressing this button lets you access exposure compensation. In order to change the exposure compensation, all you have to do is keep pressing the ‘+/-‘ button and turn the dial on the left or the right side.

Rotating the dial on one side would increase the exposure and it would reduce when moved towards the other side. Each time you move the dial by 1 step, it increases/reduces the exposure by 1/3rd. So you can easily increase or reduce the exposure by 1 stop by moving 3 steps on the dial, and so on.

You might not find this button on high-end digital cameras such as the Canon 5D Mark iii, you can simply adjust the exposure compensation by rotating the wheel located near the screen.

How exposure compensation works in each mode?

Aperture Priority: In aperture priority mode, you have the control over the aperture opening whereas the camera decides the shutter speed and the ISO value as per the available light. With the use of exposure compensation you can control the shutter as per your choice, rather than the camera forcing a specific speed. Suppose you need to click a photo at f/1.8, using the aperture priority mode the camera is giving you a shutter speed of 1/500 sec. After click the photo you realise that the photo is underexposed, you can then fix the exposure by reducing the shutter speed using the exposure compensation.
Shutter Priority: While using the shutter priority mode, you get to control the shutter speed whereas the camera decides respective aperture and ISO value as per the available light. By using the exposure compensation you get to adjust the aperture value manually, rather than the camera choosing a value for you. For example, you want to click a fast moving car at 1/1000 sec shutter speed and while using the shutter priority mode the camera is giving you an apertue value of f/4. After clicking the photo you realise that the photo us overexposed, you can fix the exposure by increasing the aperture value using the exposure compensation.
Program: In program mode the camera decides the aperture value as well as the shutter speed combination, all you get to control manully is the ISO value. With the use of exposure compensation you get to take charge over the shutter speed, though the aperture value is still defined by the camera. This is a great mode to get started if you want to leave the automatic mode behind and start learning how the shutter speed works.