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A lesson in light metering

The Digital Photography School blog has a great introductory post on different metering modes. Like the reader who originally submitted the article, I also was a little confused on what the different metering modes were when I bought my first DSLR (a Canon Digital Rebel XTi). Once I started playing with the different modes, I quickly got a feel for what they did, and I soon found myself wishing the XTi supported 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.” (link)

Without spot metering, I found myself constantly playing with the exposure compensation settings in order to get the proper exposure on one object. If the exposure compensation was off, my target object would either be underexposed or overexposed. This would result in me taking a large number of photos of the same thing, hoping that one of the shots would be just right. And, even then, it was hard to tell if I got the desired shot on the tiny LCD viewer on the back of the camera, especially if my subject was small.

Then I got my Canon EOS 5D, which does support spot metering. Take a look at the two photos below…

You can see that Abe himself is awfully bright. That’s because, at night, Abe is lit up quite well, while there is virtually no light on anything else. Using evaluative metering, the camera takes a guess regarding what the proper exposure would be by evaluating almost the entire frame. The result, the foreground is a little more visible but, the thing I want, Abe, is too bright:

Then I switched to spot metering mode. In spot metering mode, the camera evaluates the light at the dead center of the frame and sets the exposure only on that one spot. The result, Abe is properly exposed and I got the shot I wanted:

In most cases, evaluative light metering works quite well. But, if you’re in a tricky lighting situations with large variations of light throughout the frame, you might want to consider your camera’s other metering modes. For a quick explanation, the DPS article is a great start!

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