How do you use exposure lock if you use back button AF?

There's recently been quite a few threads about back button AF and I want to give it a try, but where does the exposure lock go to when you set back button AF? When shooting in AV I use exposure lock a LOT and since back button AF uses the same button, how would I do that?

I think it depends on your camera model. Not sure about the XSi, it may not support it. I don't think my XTi supported it. But if you have it, it is set via the AF/Shutter Button settings in the custom functions CnIV 1 menu and there are various settings having to do with when and how the AF is engaged and which button does AE. The manual does an okay job of explaining them but I still find it confusing sometimes.

Hope this helps.

You just keep the shutter button half-pressed to lock the exposure.

Page 158 of the user's manual covers this, but the short answer is that if you set C.Fn-10 to 1, then a half press of the shutter button will engage the exposure lock.

Thanks guys! Yea, I should have double checked the manual. Only quickly skimmed through it once, so I missed a bunch of stuff.

good info, i'm gonna engage mine to do so.

I have a 50D so the buttons are dedicated for each function, therefore no over lap, but on other models it may be a bit more tricky.

The easiest way to get an absolute exposure lock is to use the "M" position on the dial. That's what I do most of the time, and I also get a lot better exposures overall using my brain than by using the camera's brain.

SkipD wrote in post #11819323
The easiest way to get an absolute exposure lock is to use the "M" position on the dial. That's what I do most of the time, and I also get a lot better exposures overall using my brain than by using the camera's brain.

If I'm using the camera's internal light meter anyway I think AV mode allows you to be more fluid.

Sp1207 wrote in post #11819368
If I'm using the camera's internal light meter anyway I think AV mode allows you to be more fluid.

You'd be surprised how much more efficient manual exposure mode can be in quite a lot of situations. Most of the time, the light on the scene is not changing and I can leave the exposure settings the same for quite long periods of time. Usually, I use a handheld meter but sometimes I'll use the cameras meter. I do NOT "chase the needle", though, as that is quite counter-productive.

I appreciate this thread - AE/AF lock button is one feature I have trouble explaining to myself and friends on digital photo walks (and each camera model may have different physical buttons and Custom Function settings). A Nikon owner showed me where his high-end camera (I forget the model) had separate buttons to perform what the Custom Function settings mentioned above do.
Ref. My 5D2 C.Fn IV Operation/Other says (how can this not confuse anyone?)
0: Metering + AF Start
1:Metering + AF Start/AF Stop
2: Metering Start/Metering + AF Start
3: AE Lock/Metering + AF Start
4: Metering + AF start/Disable
I'm always "pumping" the shutter button 1/2 way down to re-achieve AF, and if I knew I wanted to meter on an off-subject point, mode 3 would seem to work... i.e., meter on desired point, then settle on focus w/ shutter 1/2 way down... if I indeed get it.