What Are Metering Modes?
If you read the article “how to use you camera in manual mode – part 1”, you’ll know how to utilize aperture, shutter speed, and ISO to control exposure in your camera. This article will focus on the different metering modes and how they help your camera estimate optimal exposure.
Your camera uses a light meter to measure the brightness of your subject. Depending on the metering mode selected your camera will then suggest what it thinks is optimal exposure. This will be displayed in your viewfinder using a digital scale called the “exposure compensation scale”. When you’re adjusting your aperture, shutter speed and ISO you’re trying to balance this scale with an expectation that the result will be a well exposed image. Your camera however can sometimes get its estimated exposure wrong.
What happens when your camera gets optimal exposure wrong?
Your final image will be either under- or over- exposed.
If you balanced your exposure compensation scale and your camera produced a final image that was either under- or over- exposed then it could have been that the metering mode was incorrectly estimating the optimal exposure.
This is where it is important to understand that there is more than one way for your camera to read the brightness of your subject. These settings are called the metering modes.
Your camera has three main metering modes:
Matrix or Evaluative Metering Mode: The default metering mode on most dSLRs. Matrix metering works by dividing the entire frame into multiple zones. The zones are then analyzed on an individual basis for light and dark tones. After reading the information from the individual zones, the metering system will evaluate where you focused within the frame and make it more important than all other zones. Your camera essentially looks at the light levels in the entire frame and tries to come up with an exposure that balances the bright and the dark areas of the image, with a slight emphasis on your focus point.
Matrix / Evaluative mode is great for Landscape and Seascape Photography
Matrix mode is the most commonly used metering mode however it’s important to understand the other metering modes so that you can understand when they may be more appropriate.
Center-Weighted Metering Mode: Using the entire frame to determine the optimal exposure is not always desirable. Center-weighted metering evaluates the whole frame but places a strong bias on the light in the middle of the frame while essentially ignoring the corners. Compared to matrix metering, center-weighted metering does not prioritize the focus point you selected and only evaluates the center area of the image.
Center-weighted metering may be appropriate when you have a subject in the middle of your frame with the sun behind them. You want your camera to place more priority on evaluating the light and dark areas in the middle of your frame to give you the best possible chance of obtaining a well exposed final image.
Spot or Partial Metering Mode: Spot and partial metering evaluates the light in a very small part of the frame. With spot metering this is usually 1-5% of the total frame. With partial metering this will be up to 15% of the frame. Depending on your camera’s manufacturer (check your manual), your spot may move with your focus point, or you may be stuck with it in the center of your frame.
Spot metering is a very accurate form of metering in that it will give you a precise reading for a very small part of the frame. It is very useful for shooting high-contrast scenes. For example, when you have a subject that falls into a shadow or is washed out by very bright highlights.
By default it’s best to keep your camera in matrix mode. If however you want to focus on a specific area of your frame then you can adjust your mode accordingly.
Cameras often have short cuts to let you change your metering mode. It will be a button with a picture as seen below. Alternatively, you’ll find them in your menu.