Metering Patterns

Although the job of your camera's metering system is to produce correctly exposed images, it may do so using a range of different metering 'patterns'. These patterns vary the way in which light levels are measured by the camera in order to determine correct exposure, and some are more accurate than others.

Centre-weight average

This used to be the standard metering pattern found in cameras, and is still an option in the majority of SLRs. It works by measuring light levels across the whole image area, but preference is given to the central 60% because it is assumed that that is where the main subject will be in the image. For typical well lit subjects, a pattern based on centre-weighted average can be relied upon to give accurate exposures, but it can also cause exposure error in uneven lighting situations.

Multi-zone / multi-pattern metering

These 'intelligent' metering patterns - technically referred to by the manufacturers Nikon and Canon as 'Matrix' and 'Evaluative' respectively - are the most sophisticated patterns available and make taking perfectly exposed pictures easier than ever. They work by dividing the viewfinder into various 'zones' and measure light / brightness levels in each. The zone readings are then analysed by a microprocessor and an exposure reading is set based on comparisons to model lighting situations. By doing so, the exposure reading is not overly influenced by bright or dark areas in the scene - such as brilliant blue sky - so the risk of exposure error in the image is drastically reduced.

The number of zones in the pattern varies from 4 to 16, depending on the model of camera that you are using - the more zones there are available, the more accurate the system is likely to be.

Partial / selective metering

This pattern measures light levels in a small central area of the view finder - usualy 6 to 15% of the total image area - and in doing so allows you to meter from your main subject, or a specific part of the scene, without excessively bright or dark areas influencing the exposure obtained.

Spot metering

This pattern is similar to selective metering, but it measures light levels in a tiny central area of the viewfinder - anything from 1 to 5% of the total image area. Consequently, you can use it to take meter readings from small areas of a scene, and in experienced hands it is the most accurate and useful system around.

Multi-spot metering

Some cameras allow you to take a series of individual spot readings, store each one in the camera's memory and then average them out to establish the best exposure. This is ideal in situations when you are not sure where to meter from; by metering from the lightest and darkest areas and then averaging them, you will obtain an exposure that makes a good starting point for a successful image.