Learning to use the different metering modes on your camera is a skill well worth knowing as it puts in your hands more control in how your camera approaches capturing a particular scene.Every time you point your camera at a scene it needs to take a guess at what is important to you in the picture and which part you want to be exposed optimally. The metering mode you have your camera set to will signal to the camera how you want it to approach this task.Let me explain further by highlighting three main metering modes that you’ll find on many digital cameras (note - not all cameras offer this choice although all DSLRs do and many point and shoot cameras do):
1. Overall Metering (Multi Segment/Zone Metering/Matrix)In this mode the camera attempts to take into consideration everything in your frame. Most cameras will have numerous metering zones around the frame (for example the Canon EOS 5D has 35 points that it takes into consideration).It assesses overall lighting from all these zones and takes a best guess by averaging them to decide on how to expose the shot. This mode is the one I used to leave my camera set to most of the time and it did give great results. However, at times the camera guesses wrong and it’s useful to know how to use the other metering modes below to give your camera a little more information about what you’re trying to achieve.
2. Spot Metering
This mode tells the camera to do it’s metering from a very small ’spot’ in the scene. Instead of taking information from all 35 zones, the 5D hones right in on one - ignoring all others. This is a very useful mode for tricky lighting conditions where the whole scene is either darker or lighter than the point that you want to be exposed correctly.For example in a back lit situation where you’re taking a portrait of someone whose face is a little too dark. Without spot metering in this situation you might end up with a silhouette and not be able to make out the features of your subject. Spot metering gives you very exact control when there is a very specific (and small) part of the scene that you want to get right.
3. Center Weighted MeteringOn the spectrum between overall metering and spot metering we find the Center Weighted Metering mode which takes a little from both ends of the spectrum and tells the camera to focus it’s metering decisions upon the center of your image (although a wider area than spot metering).In Center Weighted Metering the camera will take information from numerous metering points around the frame but will give more weight to those in the center. Like spot metering, this is good to use in tricky lighting situations where you don’t need to identify very small parts of the image to meter on.
The information above is from SOPM~