What is exposure compensation and how do you use it?
Exposure compensation, or Exposure Value compensation, is a handy feature that appears on many cameras. If your camera has it, you should be able to access it via the menu or by pressing the button with a small plus and minus sign on it on the back of your camera.
Exposure compensation allows you to quickly underexpose (darken) or overexpose (brighten) your shot. Unless you are in Manual mode, your camera will automatically set what it believes to be the correct exposure for the scene you are shooting. This means that it will choose a shutter speed and/or aperture that will let just the right amount of light into the lens. Most of the time, your camera will get it right, but on some occasions it is necessary for you to override it by making use of exposure compensation.
To overexpose your image, you need to move up a stop or two on the exposure dial to +1 or +2 EV. To underexpose your image, you need to move down the exposure dial to -1 or -2 EV.
Here are a few examples of when you might need to use exposure compensation:
Shooting in the snow
When shooting snow on a bright sunny day, the light reflecting off the snow may cause your camera to read the available light in the scene incorrectly and underexpose your shot. This will result in dull, grey snow in your photos. To prevent this, you can increase the exposure compensation by one or two stops to brighten up the snow. This also applies to shooting bright white subjects, such as white flowers.
Shooting against a bright or dark background
Your camera can sometimes expose for the background of your shot instead of your subject. If the background of your shot is brighter or darker than your subject then this will leave your subject under or overexposed. You can easily correct this by adjusting the exposure compensation as you see fit.
For creative effect
When shooting a portrait or still life photo, you may wish to use the high key or low key technique. High key photos feature a blown out bright white background, whilst low key shots are dark with a single light source illuminating your subject. To achieve this effect your need to intentionally overexpose (for high key) or underexpose (for low key) your shots slightly, using exposure compensation.
To find out about lots of other really useful camera settings that you can’t live without, take a look at Issue 22 of Photography For Beginners magazine (out now!).

Exp.comp.is the most used button on my camera. I use it all the time, sometimes adjusting by the minute depending on changing light conditions as i shoot. Also when daylight too harsh and contrasty i use my shadow to fall on flower/insect then crank up the exposure. Result is clear and no blow outs