Eventually, you will need Exposure Compensation to properly expose your image. In this tutorial, I will discuss what it is and when and why you need to use it.
If you have been following along with my blog this is a continuation of my basic photography series. If you haven’t read my previous article about manual mode and other topics you may want to do that.
A Little Theory
Paramount to understanding this is to understand how our photograph is exposed in the first place. Modern DSLR cameras all have an in-camera metering system. Metering means the camera will measure the brightness and from that measurement set the exposure.
In the days of film, before internal camera meters, metering could be done with an 18% gray card. This was simply a card that you would use to meter on to determine the brightness and exposure for the scene.
18% gray is neutral for all tones in the color spectrum. Reflected light from reds, blues, greens or any color is reflected at 18%. Your in-camera DSLR meter also measures all color based on 18% gray.
Exposing for White or Bright Images
White reflects more light than the other colors on the spectrum. Its reflectance is 36%. The camera, on the other hand, is reading this as 18% gray. What this means is that brighter reflectance is being UNDER EXPOSED. This is because white is being measured at 18% gray reflectance when it is actually brighter.
Take for example shooting a snow scene.
The inverse is true for night scenes. Black reflects at 9% so the image can be perceived by your camera meter to be brighter than it actually is since it measured at 18% gray, overexposing it. In this case, since it is too bright, you would use exposure compensation to reduce the exposure. Again, always review your new exposure and check the histogram
Setting Exposure Compensation
Finding the setting to change your exposure when in Shutter or Aperture mode is easy to find. You may see the below icon on your camera near the shutter release.
For others, it may be on the LCD menu settings on your camera.
For those that have the button on their camera, pressing it and turning the command dial will adjust your exposure. As you press the button and turn the dial you can see the tick mark in your meter move to the left or to the right.
If you recall, each of those ticks is a third stop or what we call an Exposure Value (EV) when metering. When you set +1 EV, you are 1 stop overexposed, while at -1 EV, you are 1 stop underexposed.
So How Does the Camera Do This?
It depends on which camera mode you are in. Remember, in Manual and Auto you will not be able to use exposure compensation. Only in Aperture and Shutter Priority modes (and Program Mode which we have not discussed yet-another topic) allow you to use this feature.
Aperture Priority Mode
In aperture priority mode the camera changes the shutter speed. With this, you can remain at the same aperture and let exposure compensation change the shutter speed.
Shutter Priority Mode
In shutter priority mode the camera changes the aperture when you adjust exposure compensation. You remain at the original shutter speed while the camera changes the aperture.
Using exposure compensation is a great feature and can really up your game in photography. The one thing I would emphasize is to ALWAYS reset the exposure compensation back to 0 when you are finished using it.
Not resetting your exposure compensation is going to be a cause for suffering trying to figure out why your next subject is too bright or dark. Just get in the habit of checking it whenever you pick up your camera and head off for a shoot, just in case you forgot to reset it. It happens.
Try out what you have learned from exposure compensation. On your next outing meter on something mostly white or bright. Check the histogram. And if too dark, add exposure compensation until it is properly exposed.
In the next tutorial, I plan on the topic of Exposure Bracketing. This is a very useful skill set so you want to be sure you Subscribe so you do not miss that installment, especially if you are interested in HDR photography.
As always, happy shooting.