Digital cameras, as well as film ones, do not always make a perfect exposure. The matter is that when the subject is very light-toned (i.e. a snowy landscape), the camera will probably underexpose and the image may come out too dark. On the other hand, if your subject is very dark-toned (i.e. a black cat) the camera will most likely overexpose and the image will come out too bright. This happens mostly because unusually light-toned or dark-toned subjects can "fool" your camera's light metering system.
Using Plus (+) or Minus (-) features for a Better Exposure
Use your camera's Playback mode to view the picture that you've just taken on the LCD screen. If the brightness of
the image is not good enough, then re-shoot with different exposure settings. Exposure compensation is the most intuitive and good working override in this situation. What you need to do is to simply set a + (plus) level to get a brighter image or set a - (minus) level to get a darker one.
Exposure compensation feature is available with most digital cameras. To access this feature just use the (+/-) button on your camera or access it from the electronic menu of the device. Exposure compensation feature is best used in Program (P) mode or in the semi-automatic Shutter Priority and Aperture Priority modes. However, this feature can be unavailable in AUTO mode or the subject-specific Program modes: the Landscape, Sports, Portrait, etc.
Even though black or very dark-toned subjects are pictured not very often, when they are, the image can come out too bright, and what was supposed to be rich dark black may be gray instead. If such situation appears, use the - (minus) exposure compensation and re-shoot the scene for a darker image.
Practice Using Exposure Compensation
Just like everything else in photography, exposure compensation needs practice. To improve your skills try taking some wide angle pictures of light-toned subjects. That can be a landscape with bright snow, water or sky. At first you'll probably see that your pictures come out to dark, which means that they are unexposed.
Set exposure compensation to a +1 level and take the same picture again. In most cases this will bring the brightness of your image to the normal level, thus, will make them better, maybe even close to perfect. This happens because with the + (plus) exposure compensation level the camera makes photos with more exposure.
However, sometimes your images can come out excessively bright. That's not a very good thing since it is preferable to keep some details in the brightest areas visible. Those can be texture in snow, for example. If you find that a +1 level of exposure compensation is too high and pictures are too bright, set a less compensation level, for example +0.5 or +0.7.
The Bottom Line
Nowadays most brightness problems can be fixed later on with different software products like Photoshop. However, it is best to get the brightness correct right away, in-camera. This saves your time later and reduces the risk of damaging pixels of the photograph. Exposure compensation is also a great creative tool. For example, you can make an image look unusually or more pleasing to the eye. While doing this remember that your pictures don't have to be technically perfect.