In-camera meters measure the light reflecting off your subject and determine the camera setting that would result in middle grey (also called 18% grey). For more information on middle grey, read “Camera Metering and 18% Grey.” Depending on the type of in camera meter, it also measures the light reflecting off the background and everything else in the frame. It averages the readings and comes up with a single exposure recommendation for the photograph.
There are several different types of in-camera meters. The four most common are Multi-zone, Partial, Spot and Center-weighted. And, of course, there’s always shooting Manual. Here, we’ll take a look at the differences between each by photographing the same scene with the four different meter readings, and my own manual reading.
I chose a white subject to illustrate how camera meters measure for 18% grey. Notice how dark the white is in the metered exposures, as compared to the manual exposure. Regardless of how bright, or how dark, your subject is, the camera meter will read for middle grey.
Middle grey aside, click the image to enlarge it so that you can see the subtle differences in each photograph. Each meter produced slightly different results.
Multi-zone metering reads several different areas (or zones) of the entire frame. It averages all the readings into a single exposure recommendation.
The specifics of zones and how each zone is weighted varies with each manufacturer. Canon’s multi-zone meter is called Evaulative Meter. Nikon’s is called Matrix, Petax calls their’s Multi-segment. I’ve also heard it called Honeycomb metering.
To get the most accurate exposure, focus on your subject first. Press your shutter button half way to get the meter reading second. The meter weighs the focused area most heavily, although the specific algorithm is kept secret.
Canon recommends their evaluative mode for portraits and photographing evenly lit subjects. It’s also helpful when you’re not centering your subject.
Partial metering reads about 8% – 15 % of the frame. It reads the center and some of the surrounding area. Partial metering gives you more control over your exposure, although it will take a little more involvement in the part of the photographer for proper use.
This is especially good for photographing a dark subject on a bright background (or vice versa) and scenes with unusual lighting.
If your subject isn’t centered, then it’s important to (1) center your subject, (2) take a meter reading, (3) engage your AE Lock, then (4) recompose your photo with your subject off center and (5) take the picture.
AE Lock is called Auto Exposure Lock. By pressing the AE Lock button (* – it looks similar to a giant asterisk for Canon Users), you’re locking in your exposure setting to properly expose for a subject that isn’t centered. Note: I didn’t do that here. To illustrate how the meters work differently, I had to use them all exactly the same way.
Spot metering takes a reading of the very center of the frame, and nothing else. It only reads about 3.5% – 5% of the frame. Using the spot meter will ensure that you get the right exposure on your subject, but there’s no guarantee that the rest of the photograph will be properly exposed.
This is a good mode for photographing small subjects that aren’t filling your frame. Such as a flower that’s not tightly composed, birds or a person in the distance.
For the most control with spot metering, use it the same way you would use partial metering: with AE Lock.
Center Weighted Metering
Center Weighted Metering gives the center of the frame the most “weight” or importance. Unlike partial metering and spot metering, center-weighted metering reads the entire frame and averages the rest of the frame with the center reading to get a final meter reading.
Center-weighted metering versus Multi-zone (Evaluative or Matrix metering):
Center-weighted deems the middle of the frame most important. Multi-zone deems the focused area most important. Center weighted is more predictable (the more you use it, the more predictable it gets) whereas the outcome of multi-zone is more difficult to predict.
Again, if your subject isn’t centered in your composition, then use the steps outlined in partial metering and use the AE lock.
Personally, I use camera meters as jumping off points for manual exposures. This is especially important when photographing high or low key subjects.
High Key: The majority of tones in the photograph are in the highlights.
Low Key: The majority of tones in the photograph are in the shadows.
Remember that the camera meter measures for 18% grey. If you’re shooting a high key photograph, you will have to adjust your camera meter’s reading to ensure that your whites are white. The same applies to low key photos: If you’re shooting a dark scene with your in camera meter, then your shadows will be too bright.