METERING MODES AT A GLANCE

HOW EACH OF THE MAJOR METERING PATTERNS ON A DIGITAL CAMERA WORKS...

PATTERN

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.

CENTRE-WEIGHTED

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/PARTIAL

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.

AVERAGE

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.

The light across the whole frame is measured as a single value. It’s a crude method, but it can be useful.

Your current focus point is one of the criteria used by pattern metering to work out the best exposure.

The small area around the AF point gives an indication of the region covered by spot metering.

The exposure is based mainly on the central part of the image, although the outer parts have an influence, too.

The graph for average metering is flat, as all areas are treated equally.

With pattern metering, the shape of the graph changes with each scene.

This graph is higher in the middle, where it’s heavily ‘weighted’.

This graph shows how spot metering concentrates around the AF point.