This is another explanation, by photographer Mark Wallace, of ‘exposure compensation’ with the added benefit of an illustration of how exactly the camera does this, when in either ‘aperture’ or ‘shutter’ priority modes.
Below are examples of both Nikon (+/-) and Canon EC (AV) buttons.
Canon-EC (or Av) button
Exposure Compensation and Spot Metering: Fixing Underexposed and Overexposed Pictures
Tony Northrup explains how to use the ‘exposure compensation’ feature, along with your digital camera’s histogram reading to correct under or overexposed images.
N.B. if using the exposure compensation button on your camera, be aware that it only works in automatic mode (e.g. aperture, shutter or programme/program priority). Alternatively you can set the camera to manual, take a shot and compensate for the under/overexposure yourself in a similar fashion.
See also video on exposure compensation with photographer Mark Wallace.
Source: Tony Northrup
Aperture, Shutter Speed, ISO, & Light Explained-Understanding Exposure & Camera Settings
Tony Northrup, author of ‘How to Create Stunning Digital Photography’, gives a very thorough explanation of ‘aperture, shutter speed and ISO’ settings.
Source: Tony Northup