METERING MODES AT A GLANCE
HOW EACH OF THE MAJOR METERING PATTERNS ON A DIGITAL CAMERA WORKS...
The default metering mode measures light distribution across the whole frame, and often takes colour and focus data into account, too. It then calculates whether the scene needs to be made brighter or darker before it arrives at a suitable exposure for the shot.
This mode measures the light across the whole picture area, but strongly biases the resulting reading to the centre of the viewfinder. On more advanced digital cameras, you can change the size of this central area, and hence affect the overall bias.
Spot metering only measures the intensity of light over a small circular area around either the active AF point or the centre one, depending on the camera. The Partial mode available on some cameras is similar, but measures a slightly larger area.
This is a variation on the centre-weighted mode that’s only available on some cameras. It measures light evenly across the whole frame, which makes it the least sophisticated metering system of all, but it can be the easiest for experts to interpret.