7.8. Metering patterns

Unlike human eyes and brains, which can interpret the importance of various sections of a scene, a camera simply detects a rectangular field of light reflected off objects. It has no idea what's important and what's not. Consequently, a number of different ways or patterns of measuring ambient (available) light levels have been developed by Canon and other camera makers. The application of these patterns depends on the camera model, user settings, and whether ambient light or flash is being metered.

7.8.1. Ambient metering and metering patterns

All EOS cameras contain light meters tucked away inside the top of the viewfinder (section 5.8). These electronic devices measure light levels and are used by the camera's computer system to set the exposure automatically.