These days most digital SLRs offer multiple methods for metering the light in a scene. The most common method includes Multi-segment, sometimes called “matrix” or multi-zone metering.
This system divides the screen into multiple (the actual number varies by camera model and manufacturer) segments. The camera’s CPU automatically determines the overall lighting level, including front and back lighting, and sometimes the color in each portion and compares it to a database of similar scenes to determine the exposure.
Some systems also integrate the data from the focusing point used, subject size, and, distance. For many cameras this is the default settings, and works fine for the average photograph and it’s why I use it most of the time.
This photograph of the Acapulco Yacht Club was made using the Canon EOS 5D’s Evaluative metering system that links to the camera’s nine autofocus points. The Program mode exposure was 1/500 sec and f/10 at ISO. ©2006 Joe Farace
Center-weighted: In this mode, the camera’s metering measurement is heavily weighted (75-80%) toward the center of the focusing screen and this system was an improvement over early built-in meters that took an average of all the light values in the viewfinder and were heavily influenced by extremely dark or light areas on the edges and corners of the photograph. You should use Center-weighted metering when the main subject covers a large portion of your photo. This mode does not compensate for backlit scenes, but the next one does.
Center-weighted, or Center-weighted average metering as Canon calls it, for this EOS 20D shot where the subject fills the frame. It was captured in Manual mode with an exposure of 1/125 sec at f/10 at ISO 800. Why the high ISO? I was trying to balance both depth-of-field (small aperture) with the ability to minimize camera motion that is exaggerated in macro photography such as this. © 2005 Joe Farace
Spot metering: When spot metering, brightness is measured only within a limited area (often one to three percent) within a circle that is shown in the center of the focusing screen. You can use this type of metering for backlit scenes by placing the sport on the subject and not the background. Photographing a performer or a speaker on stage that’s illuminated by a spotlight is a good example of where spot metering can be a godsend.
Spot metering is really important for runway fashion photography that must almost always be captured with available light and the spotlighted model is often set against a dark, sometimes, black background. For this shot at New York’s Fashion Week I used an Olympus E-1 with an Exposure of 1/250 at f/3.5 and ISO 400 in Shutter Priority minimize subject motion and spot meter mode to give me an accurate exposure. ©2003 Joe Farace
Joe Farace is co-author of “Better Digital Available Light Photography” along with Pulitzer Prize winning photographer Barry Staver. It is published by Focal Press and is available in all the best bookstores, including Barnes & Noble and Amazon.com.