Okay, so I have been choosing my own focus points , but I keep reading about "back button focus" and I can't quite get my mind around it...can anyone enlighten me a little?

Do you use it and what is your preferred method of focus? Thanks!

Basically what "back button focusing" does is moves your focus to the * button on the back of the camera, instead of having the shutter release button activate your focus and shutter. It separates them so you can shoot faster, and you can recompose a shot, while holding your focus. Personally, I use it and I have found that it allows me to shoot much faster.

I love the back focus button... for those exact reasons

Have to be careful though if you're just out and about and hand your camera to someone to snap a picture of you... They won't figure it out!

i'm a recent convert to the back focus button. greta and i were doing a shoot and swapped cameras for a moment and she had hers on that setting. i loved it! i have WAY less photos turn out OOF. i give it

I have heard explanations on podcasts and such, but < can't get my mind around exactly how and when to implement it??

DUH

are there any videos out there actually showing it?

ron, what this does is simply move your focus activation from the shutter button (where you press it half way down) to the back of the camera (the * button)

as people have said above, it makes for much quicker and accurate focus, without mistakenly changing the focus before a shot while recomposing. takes a bit of getting used to but you'll find it much more functional than the "old" way

It is set via Custom Functions in the menu.

I've been wanting to try this for a while. What are the C.Fn settings?

C.Fn 4. Set to option 1 for back button focus. This also sets your AE lock to the shutter button (so half way down on your shutter button holds your metered exposure in AE modes.)

Thanks Trevor! For some reason I knew you would answer my question.

OMGOSH!!! I 'm so in LOVE with this function! Bernadette, thanks SO much for starting this thread. I can't wait to try this out on Sunday!

It's the one single best technical change I ever made as a photographer. Give yourself 8 hours of shooting with it though...it's a hard adjustment for the first few hours. Once you figured it out, you will never go back.

Oh and (this is MAJOR) make sure you use "AI Servo" when you aren't shooting flash and have adequate ambient light to focus in. (When you are shooting flash or are using the flash focus assist light, you should use One Shot or you won't be able to trigger the Focus assist light)

Let us know how it goes!

It isn't necessary to shoot AI servo... I use 1 shot all the time since I'm not tracking quick moving subjects. Just sayin...

I pretty much leave mine on 1 shot all the time. I also don't track quick moving subjects, and its one less thing to worry about when you are going inside and outside several times in the same wedding or portrait session.

Then you are missing out on the best part of back button focusing in my opinion. Because it acts like One shot....you can release the back button whenever you've found your focus...OR you can hold it down to track. It's super good for low DOF stuff. Seriously...try it out. I think it's the best reason to use bb focusing.

the 40D, ID series cameras have their own dedicated AF-start button for the thumb. Im pretty sure we will see one for the new 5D release end of the year.

I use it and love it.

Ever tried taking self-portraits with the backbutton set? its quite... interesting

and the decicated focus button is in a much more awkward place than the * button on the 1D (pre Mark III) series cameras and all other EOS cameras

If you set your camera on Continuous focusing mode, even the Back Button will possibly create the same problem... right?

My question is... How does utilizing 2 buttons make things faster than 1 button? Aren't they doing the same thing? Where does the advantage occur?

Thanks for your time ; )

i want to know this too...I have been thinking of trying this and it seems like an extra step for every shot...maybe I am missing something...I understand the advantage of separating the metering and focus point for exposure/focus quality....but it doesn't seem like it would speed you up...

I read about back button focusing on here a while ago and I love it. I agree you have to practice for quite a while to get used to it, but it's great once you do... For me the benefit is being able to recompose and shot a scene over and over without having to refocus, it's so much faster and you aren't worried about re-focusing each time. It is hard to understand unless you've tried it. I tried explaining it to a photographer friend for about 20 min and he still didn't get what I was saying.

+1 about AI servo working better, just keep your thumb pressed on the back focus button and follow the running 2 year old, haha. Works great! But I mostly use one shot.

I just received my 70-200 VR lens the other day, and the manual says that VR will not work when using the back Focus Button. Has anyone felt like with this kind of telephoto is when they want to utilize this function the most?

Just curious?

What I like is, in situations where the focusing is difficult, and I have a zoom lens on (70-200, etc), I can zoom in on the person, focus, zoom out and then take the shot, and the exposure is set for the whole scene, not the zoomed-in part.

The only difficult thing with back-focusing is on IS lenses, you have to hold the focus button down to engage the IS, so if you're waiting for a shot, you have to hold that button down AND the shutter to get the shot you want.

not true (at least on canon cameras - well, at least on 1D bodies) the shutter button does activate IS even when using back button focus.

Yes, this works on the little Rebel XTi as well. Both the shutter button and the * button engage IS.

Specific combination is XTi with 70-200 2.8 IS. Don't know if all combinations would have the same result. I would think/hope they would.

using it you can forget that the AF/MF switch on the lens exists. Don't hit the * button and you have manual focus.

Even more useful when not using manual exposure. Imagine you are in Av mode and want to meter off one part of the scene and focus on another. You would have to point the camera to get exposure and hit the * button to lock it in. Then move the camera, still holding that * button to keep the exposure locked as you move to focus, then half press the shutter to lock focus. Then, while holding both the shutter and the * button, you can frame your shot, then fully press the shutter to take the picture. In 5 seconds the camera resets, and you have to preform all those steps all over again.

With focus moved to * button, you can focus first, then let go of the * button. You are done being concerned with focusing. Then, you can expose the way you normally would...if you are in Av, Tv, or P, you can lock in exposure by half pressing the shutter button (this function is moved here when making the switch).

Of course, with auto exposure you would have to keep re-locking the exposure or just trust the camera to do the right thing. Personally, i use manual exposure all the time, so this becomes a quick step to lock focus so I can forget about it, then another quick step to manually dial in exposure so I can forget about that too, then I can take as many frames as I want, and if i need to re-focus, just a tap to the * button does it.

Its really not that hard, and as noted above, a few hours of practicing with it you'll never go back. Just like the PC users that give macs an honest try (sorry, i couldn't resist )

+1 I can't imagine shooting any other way. The idea of trying to use auto-focus lock or using a selective focusing spot sounds like a real pain in the ass.

Say you have a bride and you want her on the left side of your shot, focus on bride, readjust your composition, set your exposure for the scene, take photos. Bada Bing Bada Boom!

Couldn't have said it better myself! Excellent explanation.

I also cannot imagine shooting any other way! It bugs the crap out of me when I pick up someone else's camera and it's set to "the old" way.

For anyone still wondering why use this function. Just think about every time a moment was happening, your focus was good, and you went to grab the shot, but instead of getting the shot you got your camera refocusing. Resulting in either a blurry image or a missed moment.
Moving the focus to the back makes it so the camera af only goes when you tell it to.

its funny becasue i think these threads recycle on a 6 month basis. when i first joined here, that was a hot topic and i tried it - now its just natural to me when i use AF, and it feels unnatural to not use it. although i still prefer MF.

and i seriously recommend it to everyone.

i use it. i love it