1.When to use Exposure Compensation
The camera’s metering system is vital when taking pictures. It works out how much lighting is necessary when entering the camera to correct exposure. The problem with metering is that it takes an average reading, this reading is assumed to be a midtone or halfway between white and black.
When shooting portraits, light skin tones can easily trick the camera into underexposing the shot. You’ll notice this is when shooting a full-face photo or when there are lots of white in the scene, brides at weddings are a good example of this.
2. Aperture Advice
When shooting portraits, it is best to have a wide aperture of around f/2/8-f/5.6 to capture a shallow depth of field, so the background behind the subject is blurred nicely, which will make them stand out better. Shoot in aperture priority mode to control the depth of field as in this mode your DSLR will set the shutter speed for a correct exposure. The specialist portrait lenses tend to have a wider maximum aperture from f/1/4 to f/2.8 in order to blue backgrounds further.
3. Shutter Speed Setting
When setting shutter speed, factor in your lens focal length otherwise camera-shake and blurry images will become an issue.
Make sure your shutter speed is higher than your effective focal length. For example, 20mm use a 1/250 second shutter speed or faster. This also means that you can get away with slower shutter speeds when using a wide-angle lens, such as 1/20 secs with an 18mm focal length.