Exposure Compensation is a neat little setting that you can use to help your camera make better exposure decisions. Depending on the camera you have, it can work in any mode that you choose to use, except Manual mode. If you are making images and they look over exposed (to bright) or under exposed (to dark) you can adjust the Exposure Compensation to help bring the exposure inline with what you expect or want it to be. You might even find that you prefer to leave it on a particular setting. For example, I leave the exposure compensation on my cameras set at -0.7 most of the time. I like slightly under exposed images and I find that most cameras over expose just a little for my taste. Leaving the Exposure Compensation set all the time allows me to walk around with my camera in Aperture Priority mode, the mode I most often use, ready for any images that might present themselves.
Using Exposure Compensation is pretty easy. All you have to do is dial in the amount of compensation you want. The tricky part is knowing how much compensation you want to add or subtract. As with most things in photography you will get the hang of it with practice. Start by making an image and look at it on your camera’s LCD screen. Are you getting some “blinkies” (flashing from white to black) in the highlights? Is there very little detail in the shadows? In either situation you might be loosing detail where you might want it later.
To correct the over exposure of the highlights use the negative (-) side of the scale. This will darken your image giving you details in the highlights. For an under exposed image use the positive (+) side of the scale to brighten your image. Make another image and see if you like the results. Repeat if necessary until you like the exposure you are getting. Any easy way to think about this is (-) takes light away and (+) adds light.
I test every camera that I use to make sure that I am getting the exposure that I expect. This is important because the camera should give you the exposure that you want when you make an image. If the camera is not giving you the exposures you expect then Exposure Compensation will help. One word of caution, if you adjust the Exposure Compensation to one extreme or the other be sure you set it back to where you normally leave it. This will insure that the next time you use the camera your exposure will be close to where you think they should be.