Digital cameras use sophisticated metering systems to decide how much light there is in a scene.

This post explains the basics of how to use the three types of metering systems found on most digital cameras: 3-D Matrix metering, Centre-weighted metering and Spot metering.

3-D Matrix metering (also called Evaluative metering)

What is Matrix Metering?

The camera sets the exposure automatically to suit the scene, taking into consideration both dark and light area’s.

The majority of digital cameras offer a sophisticated metering system that is divided up into tiny segments. Each segment is analyzed individually and the results compared to a database of thousands of scenes stored in the camera’s processor. This helps the camera identify which kind of scene has been photographed and provide an appropriate exposure. This system works extremely well under most lighting situations.

How does it work?

Matrix metering works by dividing the frame into several small zones and taking separate light readings from each one. The camera then guesses which parts of the scene are important and exposes accordingly. For the most part, it does a pretty good job at picking the correct exposure.

When should I use it?

Matrix metering is good for evenly backlit subjects like portraiture and landscapes. It’s also the best one to use when you’re not sure which metering mode to use.

Centre-Weighted Metering

Many digital cameras offer a centre-weighted metering option for setting the correct exposure for a scene. This metering system gives more emphasis to the brightness of light in the centre of the frame, where, as with the focus, the main subject is assumed to be. Using the centre-weighted metering method takes a little practice to get right. It is also prone to being fooled by off-centre subjects or large areas of extreme light or dark.

Center weighted metering would be effective when you have a bright background or backlit subject. For example, if you were taking a photograph of a persons face on a sunny day at the beach. You wouldn’t want the strong background light, or the white sand, to effect the exposure on their face. As long as the persons face was correctly exposed, that’s all that matters. It’s times like this, you would choose center weighted metering.

Spot-Metering

Some digital cameras also offer the spot-metering method of exposure calculation. In this method the camera measures the brightness of a tiny area at the centre of the frame and uses that to set the exposure. Spot-metering requires practice to master. It offers the photographer great flexiblilty in measuring the exposure in a scene.

Spot (Nikon) or Partial (Canon) metering should be used when you want to take an exposure reading on a specific area. It takes the reading from a very small area in the middle of your composition.

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