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Spot metering is my preferred metering mode on the Canon 50D. This allows me to nail the exposure first time -- 99% of the time -- by using AE-lock on my subject and applying the desired amount of exposure compensation. However, I find this too slow for some situations, so would like to learn to use one of the "full frame" metering modes (i.e. Evaluative or CWA).

I have tried using both of these modes. On the whole, I found Evaluative to be unpredictable. I found myself having to second-guess when and by how much the camera had automatically added exposure compensation. On the other hand, I found CWA to be much more predictable, but slower as it was still necessary to AE-lock and recompose for off-centre subjects.

It seems that Canon designed Evaluative metering largely as a replacement for CWA, and that by not using this, I would somehow be missing out on much of the ability of my camera.

How would I be better investing my time?

a) Using Evaluative metering and learning to recognise how it responds in certain situations so that I can second-guess it.

b) Using the much simpler CWA metering and learning to read the scene to determine the required amount of exposure compensation.

If only Canon had an "active focus point weighted average" mode, it would be perfect!

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This isn't really an answer, but it might be faster to work in manual mode with spot metering, then at least you can skip the "AE-lock" step and just dial in your exposure compensation directly using the aperture/shutter dials. As an added advantage, it may help you keep conscious of what choices you are making in terms of f-stop and shutter speed. –  David Rouse May 31 '11 at 11:53
    
Thanks, I do this sometimes, but find that it takes longer to adjust two dials than it does one. My goal here is to decide on a metering mode that can be used when there isn't time for spot metering (e.g. candid shots). –  gjb May 31 '11 at 14:10
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4 Answers

up vote 9 down vote accepted

Metering will always be trial and error, because the camera assumes everything you're shooting reflects 18% of the incoming light back at the camera. It has no way of knowing whether your subject is white or grey, or even what part of your scene is the intended subject!

The closest the camera can get to knowing the latter is by looking at the currently selected focus point, as you suggest. In fact some Canon bodies do offer spot metering linked to the active focus point. I suspect it's only on the more expensive models. Edit: yes it seems to be just the 1D/1Ds models. And it's only activated when you're using a subset of the 45 AF points, which is disappointed (you'd think it could use the closest spot metering point when you have all 45 activated).

Contrary to ElendilTheTall I use Evaluative mode almost exclusively (no I don't use the camera on auto ;). The reason for this is I don't want to be constantly recomposing to meter. Also whilst Evaluative might not get it right as much as spot metering, but when spot metering gets it wrong, it can get it wrong by a huge margin. Example, if you happen to have a deep shadow in the centre of the scene you'll massively overexpose.

At the end of the day metering is fixable in post as long as you're close, unlike for example, focus. So when shooting quickly I concentrate on nailing the focus, even if it means the metering is off. Evaluative allows me to do this. If I'm not shooting quickly I'll bracket exposure or use manual to get the exposure exactly how I want it.

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Thanks, some useful points here. Are there times when Evaluative metering catches you off-guard, or would you say it is fairly easy to learn how it behaves in different situations? –  gjb May 31 '11 at 14:19
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It still gets it wrong, usually when a dark subject fills the frame, or when the scene is more reflective than average (i.e. snow on the ground), or when you pan up and get a lot more sky in shot. But because it uses more of the scene to meter, it's less sensitive to slight changes in composition, making it more predictable in general. –  Matt Grum May 31 '11 at 14:44
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I stick with CW most of the time, and for the rest go with Spot. Evaluative just takes too much of the scene into account for a good exposure (in terms of creativity) for my liking. To me, Evaluative metering is there to help the folks who keep their camera on Auto.

I suggest you go with CW and learn to read the scene, as you say. You shouldn't have to be second guessing anything. Of course, this is all subjective anyway; many people might prefer Evaluative metering. You could set yourself a challenge and take shots for a week using only one metering mode, then repeat with the other, and see which one you prefer.

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+1 My preference as well. It is not that EM takes too much of the scene into account, but rather that you don't know what exactly it does with the information! CW considers the whole frame as well, but is predictable. –  ysap Jun 3 '11 at 16:15
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Sorry to add an answer to my own question, but I have just found the following information from Canon to be useful:

The trouble when using exposure compensation with evaluative metering is that you don’t know if the metering has already compensated for the conditions. If it has, and you dial in even more exposure compensation, then the exposure will be wrong. Equally, if you assume that the camera has got it right, but it hasn’t, then you will also have a badly exposed picture.

The solution, as with so many things photographic, is experience. After a while you will learn to recognise the types of scene which evaluative metering handles well, and those that it does not.

When you change to a different camera, you will have to learn all over again, as the number of metering zones can change the results.

Centre-weighted metering takes a reading from all of the framed scene, but with more emphasis on the central area. It was one of the main metering modes on Canon FD cameras, which came before the EOS range. Centre-weighted metering was originally included in EOS cameras to help FD users make the transition, but seems to have become a permanent feature.

Unlike evaluative metering it makes no attempt to analyse the scene, so you can apply exposure compensation in the knowledge that the camera has not made any adjustments of its own. For this reason, centre-weighted metering is often better than evaluative when you know that some level of exposure compensation is needed.

Source: Canon Professional Network

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answering your own question is perfectly fine here (assuming you have something smart to say, that is...). No need to apologize. –  ysap Jun 3 '11 at 16:11
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If only Canon had an "active focus point weighted average" mode, it would be perfect!

It does. It's the Evaluative Metering indeed. It evaluates the entire scene, but it weighs the exposure more on the active focus point(s).

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