Exposure lock Vs Exposure compensation Vs metering modes: when to use what?

[JClishe]

I'm trying to understand the practical differences between the metering options that are available. If my camera isn't auto-selecting the correct exposure settings that I need, my options as I understand them are a) adjust using exposure compensation, b) meter off-scene, use exposure lock and re-compose, or c) switch to a different metering mode (spot, partial, etc).

So what are the pros and cons, and most practical? Seems like metering off-scene and using exposure lock is the easiest, because you can do it with your thumb without looking up from the viewfinder.

I also read somewhere that some people leave exposure compensation set -1/3 stop all the time to protect against blown out highlights. Is this a practical suggestion?

 

[musicaleCA]

Leaving your EV comp at -1/3 is very useful in daylight, or whenever you're at risk of having blown-out highlights. Not so useful in really controlled conditions (in which case you should have enough control over the light to expose everything correctly). Personally I never use the centre-weighted or partial metering modes; I either use spot or evaluative. Spot metering is used most easily when you have a grey card to meter off of, or something that you know is roughly 18% grey. You should read-up on how to use the Zone System when using spot metering though; you can really meter off of anything, and then place it where you want in the dynamic range of the camera with EV comp.

Spot metering something that won't be in the image at all, now that's a little confusing. I don't see why you'd ever want to do that. *scratches head*

Evaluative metering is usually best used when running-and-gunning, or when you don't have time to set exposure (say, if you're taking candids; you don't have a split second to deal with exposure, it's mostly guess-work, though thankfully with the advent of light meters and AE on digital cameras, it's a whole lot easier to just point, shoot, and trust you got an exposure that's workable).

 

[Big Mike]

Another method is just to take a test shot, read the histogram, adjust your exposure and take another shot.
Much of the time, I'm not even looking for 'proper' exposure, but an optimum exposure for further editing.
Read THIS, then THIS.

Also, I believe your 50D has a mode called Highlight tone priority, which sets the exposure to be just under blown out highlights...basically the same idea as the link above.