Metering Explained

Tutorial :25 - Metering Explained

Every camera has a built-in light meter, and metering is the process of how your camera determines what the proper exposure should be for any scene. There are a few methods of doing this and most cameras today allow the users to select their preferred metering mode. Among the most common are: Matrix metering, Center-weighted metering, and Spot metering. Here’s how to choose the best metering mode for your shot.

Matrix Metering

Also known as multi-zone, multi-segment, pattern or evaluative metering, matrix metering divides the entire frame into a matrix, samples the light from every part of the matrix and uses it to determine the best exposure that will balance the dark and bright areas of the scene.

Matrix metering is the most complex of all metering modes and is normally the default mode as digital cameras today often employ very sophisticated metering algorithms. Matrix metering is best used when your scene is mostly evenly lit, especially when shooting outdoors or landscape photos.

However, if may not be the best metering mode to use if you want precise control of your shot. Since matrix metering evaluates the entire scene, you may find that exposure can vary from shot to shot even if you move the camera a little to recompose. Also, matrix metering algorithms can be different for different camera makes and models. Some cameras may place emphasis on the exposure of the focal subject, while others can un-link metering and focus points.

In this shot, matrix metering was used and the camera tried to balance both subject and background exposure for a more evenly lit photo.

Spot Metering

Spot metering, also known as partial metering, is the direct opposite of matrix metering. It is the most precise of metering modes and will measure exposure only from a small spot right at the center of the frame.

Spot metering is used when you want total control of the scene and only want exposure metered on the exact subject point. In addition, some cameras with multi-area AF modes can link their focus areas to spot metering, so that you can apply spot metering directly on the subject that the camera has focus lock on, which is quite helpful when trying to meter on a moving subject and you want to keep the subject metered regardless of background.

Spot metering however, is the most difficult to master, and is often only used in when shooting in challenging conditions where you might want to meter and re-compose your shot in conjunction with the AE Lock function.

Center-weighted Metering

Center-weighted metering sits in the middle of matrix and spot metering modes. Like matrix metering, center-weighted metering measures light throughout the frame, but provides greater bias towards the center.

Center-weighted metering works best when you’re more concerned about subjects around the center being properly exposed without being influenced by the exposure of the background, such as when shooting portraits. It is useful when you have a subject that highly contrasts with its background, such as people against a setting sun, which can be confusing to matrix metering as the camera will try to expose for both light and dark areas, either overexposing the sky or underexposing the subject depending on the focus area mode used.

Center-weighted metering often produces the most consistent metering, though it is not as sophisticated as matrix metering in more advanced cameras.

Unlike the spot metering example before, which metered only the exact dark grey point that was focused upon, or matrix metering, which tried to balance the exposure of the entire scene, center-weighted metering gave priority to the subject without being affected by the background. For this series of examples, center-weighted metering produced the most even exposure for the subject, at the expense of background lighting.

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