Back Button Focusing

[megdh525]

I recently bought a Canon T2i and am playing around with the different settings, but one thing I cannot figure out is Back Button Focusing. Can somebody please explain how I can do this with my camera, or is it not possible? I know it has something to do with the asterisk (*) button. Also, is it possible to use it in Manual mode? I thought the * was supposed to show up in the viewfinder when you are using back button focusing, but I don't see it. Thanks in advance for your help!

[karen_s]

Unfortunately this article is not specific to the T2i but it might help explain how back button focus works in the world of Canon ...

Canon Digital Learning Center - Back-Button Auto Focus Explained

I use back button focus with my 50d and love it. It was a bit awkward at first but I grew to love it and now shoot using the technique all the time. And yes, it works in Manual exposure mode along with a few others.

Hope the article helps.

[Jim Bryant]

That's the only AF mode I shoot in. Unfortunately that function is not available on my MK II Ds model and I keep forgetting.

[pakyooh]

Really? 5D MK II doesn't have this feature?

Originally Posted by Jim Bryant

That's the only AF mode I shoot in. Unfortunately that function is not available on my MK II Ds model and I keep forgetting.

[inkista]

Originally Posted by megdh525

...Can somebody please explain how I can do this with my camera, or is it not possible?

You can do it. It involves messing about with the custom functions. On the T2i, it would be C.Fn IV.9. If you set it to any of the settings other than 0, you will have back button autofocus.

I know it has something to do with the asterisk (*) button.

Yes. You're basically moving one of the functions from the shutter button half-press to the * button, and replacing the default AE lock function.

Your four settings are:

0: AF/AE lock
1: AE lock/AF
2: AF/AF lock, no AE lock
3: AE/AF, no AE lock

What's before the slash is what your shutter button half press triggers. What's after the slash is what the * button (or AF-ON button if you have one) triggers.

Moving AF to the * button is "back-button autofocus."

Also, is it possible to use it in Manual mode?

Yes.

I thought the * was supposed to show up in the viewfinder when you are using back button focusing, but I don't see it.

No. The * in the viewfinder still indicates AE lock. The round circle for AF confirmation is still for AF. The only thing that's changed is which button triggers which function.

Originally Posted by pakyooh

Really? 5D MK II doesn't have this feature?

He means the 1Ds Mark II. The 5D Mark II does back-button AF just fine. Jim--really? dpreview's saying C.Fn.04 on the 1Ds Mark II does the back-button thing.

[David Taylor]

I love the back-button focus option, and have it set on both my 5D Mk 2 and 7D. Great for wildlife. I set it so that only the back button can activate focus lock, and the shutter only trips the shutter. That way I can achieve focus lock on an off-centered subject with my center AF sensor (higher accuracy than any other AF point), release the back-button focus button recompose and hit the shutter button to take a pic. Very fast and accurate once you get used to it.

[maturner525]

Thank you, Thank you, Thank you!!

I have just recently read about back button focusing and didnt know how to set it up. This will make my life so much easier. I stay on AI Servo for AF as I shoot alot of action photos. This is great! I tried it at home and it works perfectly.

Mark