What is Back Button Focus all about?

Started Mar 25, 2014 | Discussions
BobT Forum Pro • Posts: 13,192
What is Back Button Focus all about?

I see a lot of you use this.  So what is it?  Why would I ever want it?  And how (step-by-step) would I go about getting it?  I shoot with a T2i.

Thanks

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scorrpio
scorrpio Veteran Member • Posts: 3,595
Re: What is Back Button Focus all about?
4
ColinJennings Junior Member • Posts: 40
Re: What is Back Button Focus all about?
1

I just got my first DSLR on Feb 28th for my birthday.

One of the first things a friend got me to do was turn on back button focus and I am so glad that I did. Why?

1. Makes you think more about composition. Get focus then move the camera to get composition.

2. Lets me use rule of thirds much easier

3. Allows me to always use the center focus points which on most cameras is the best.

4. I find it is just easier to get a preview of my exposure. I'm not as tempted to just half click then full click.

5. In live view mode it allows me to focus, zoom in, focus again then shoot.

The best thing is when I hand the camera to my wife and she puts it into auto the camera goes out of back button focusing.

It is true all this can be done without back button focus but it is just easier and to me now second nature. I'd never go back... errr wait.. you know what i mean

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WilbaW
WilbaW Forum Pro • Posts: 11,562
Re: What is Back Button Focus all about?
1

BobT wrote:

I see a lot of you use this. So what is it?

Using a button on the back of the camera to trigger autofocus instead of it happening on a half-press of the shutter button.

Why would I ever want it?

When you don't want the system to autofocus every time you press the shutter button. For instance, I used it recently when I was shooting a couple of pelicans on a rock with a long lens on a tripod. I wanted to focus in One-Shot, then reframe, then sit back and wait for an interesting moment. I needed the focus to stay where it was no matter what I did with the shutter button. (I could have switched the lens to MF, but then I'd have to muck about switching it back if I did need to focus again.)

Many like to use it all the time with AI Servo, so they have both continuous or locked focus available, with just one button to press. I think a lot of people like it because it means they don't have to master the fine control of the shutter button half-press that you need to do focus-and-recompose and to hold focus between shots.

And how (step-by-step) would I go about getting it? I shoot with a T2i.

Set custom function IV-9 "Shutter/AE lock button" to 1, and from then on press the "*" button to trigger autofocus.

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Ken53 Senior Member • Posts: 2,128
Re: What is Back Button Focus all about?

BobT wrote:

I see a lot of you use this. So what is it? Why would I ever want it? And how (step-by-step) would I go about getting it? I shoot with a T2i.

Thanks

Here is a post from a specific T2i forum that should help.

http://www.t2iforum.com/general-discussion/back-button-focusing-on-the-t2i/

Ken

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RS_RS Senior Member • Posts: 1,788
Re: What is Back Button Focus all about?
2

BobT wrote:

I see a lot of you use this. So what is it? Why would I ever want it? And how (step-by-step) would I go about getting it? I shoot with a T2i.

Thanks

Strange question from a Forum Pro, especially since a search would turn up several threads explaining the technique.

MOD Olga Johnson Forum Pro • Posts: 23,963
Re: What is Back Button Focus all about?
3

RS_RS wrote:

BobT wrote:

I see a lot of you use this. So what is it? Why would I ever want it? And how (step-by-step) would I go about getting it? I shoot with a T2i.

Thanks

Strange question from a Forum Pro, especially since a search would turn up several threads explaining the technique.

Forum Pro only relates to number of posts one has written.  Forum Pro does not mean photography or equipment Pro.

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Olga

MOD Olga Johnson Forum Pro • Posts: 23,963
Re: What is Back Button Focus all about?

In addition to other reasons folks have given you, back button focus allows me to use my thumb and keeps my index finger useful for the shutter alone.  I have a tremor in my hands which sometimes results in an inadvertent refocus of a scene.  That never happens when I can use my thumb for the focus.  I find it especially useful when shooting in Servo mode.

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Olga

OP BobT Forum Pro • Posts: 13,192
Re: What is Back Button Focus all about?

Thanks for both comments, Olga.

I happen to be very comfortable with 1/2 press technique(using center point---then recompose). I've done this for years and for each and every shot that I take.  It's an automatic reaction anymore.  Is the back button still of benefit to me?  Does the Back Button Focus allow for keeping the focus set no matter what else one does; eliminating the necessity of re-1/2 pressing the shutter button?

I'm trying to find a real useful reason for me to use this.  Just not sure of it's benefit to me personally.

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yousaf Senior Member • Posts: 1,083
Re: What is Back Button Focus all about?

there is a video "Back Button Focusing with the Canon T4i(650D) and T5i(700D)". I would recommed you to watch it.

MOD Olga Johnson Forum Pro • Posts: 23,963
Re: What is Back Button Focus all about?

BobT wrote:

Thanks for both comments, Olga.

I happen to be very comfortable with 1/2 press technique(using center point---then recompose). I've done this for years and for each and every shot that I take. It's an automatic reaction anymore. Is the back button still of benefit to me? Does the Back Button Focus allow for keeping the focus set no matter what else one does; eliminating the necessity of re-1/2 pressing the shutter button?

I'm trying to find a real useful reason for me to use this. Just not sure of it's benefit to me personally.

Bob, you are the only one who can answer that question.  

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Olga

RS_RS Senior Member • Posts: 1,788
Re: What is Back Button Focus all about?

Olga Johnson wrote:

RS_RS wrote:

BobT wrote:

I see a lot of you use this. So what is it? Why would I ever want it? And how (step-by-step) would I go about getting it? I shoot with a T2i.

Thanks

Strange question from a Forum Pro, especially since a search would turn up several threads explaining the technique.

Forum Pro only relates to number of posts one has written. Forum Pro does not mean photography or equipment Pro.

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Olga

Quite so.

dlinney Regular Member • Posts: 217
Re: What is Back Button Focus all about?

1) Suppose you want to take a series of shots of a person giving a speech. You want the subject off-centre. With normal shutter button controlling focus I have to position, half-press, recompose, fully-press for each of the shots. With back button focus: I position (for focus) and hit */AF-On button (don't have to hold it down), recompose hit shutter button to take picture, hit shutter button to take next picture, hit shutter button to take next picture, ...etc. - no need to recompose between shots.

2) I have a bird in a tree and camera tends to lock focus on branches towards the front. Each time I take a picture I have to juggle the camera to get it to lock onto the bird rather than a branch. With back button focus I only need do that juggling once and the focus stays put however many shots I take.

3) I want to take a series of shots with different DoF - again with subject off-centre: I can lock focus by hitting back-button, then take several shots in quick succession with different apertures without having to refocus / recompose each time.

If you took back-button focus away from me now I would absolutely despair. It takes a little time to get used to it but once it becomes second-nature it is far superior (for me) to using focus on the shutter button.

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Derek

Hank3152
Hank3152 Forum Pro • Posts: 13,499
Not really that strange..........

RS_RS wrote:

Olga Johnson wrote:

RS_RS wrote:

Strange question from a Forum Pro, especially since a search would turn up several threads explaining the technique.

Forum Pro only relates to number of posts one has written. Forum Pro does not mean photography or equipment Pro.

Quite so.

Well, in Bob's defense, judging by threads started, he's more of an inquirer ........

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Regards,
Hank

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OP BobT Forum Pro • Posts: 13,192
Re: What is Back Button Focus all about?

Derek,

Excellent examples of applications for the Back Button Focus.  Just one additional thing.  Once you hit the back button and lock your focus, can you take your finger off of the back button; since the focus will be locked no matter what other settings (aperture, ISO, shutter speeds) you might wish to apply?  If so, how do you reset the the back button for other shots?  Just hit the "*" button?

Based on your samples, I think I'll try it out.

Thanks

Bob

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OP BobT Forum Pro • Posts: 13,192
Re: Not really that strange..........
1

Hank,

CORRECT......Far from an expert in these forums.  But very much an inquirer.  Thanks for clearing that up.  Couldn't have done better myself.

Bob

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Phhoenyxx
Phhoenyxx Senior Member • Posts: 2,507
Re: What is Back Button Focus all about?

BobT wrote:

Derek,

Excellent examples of applications for the Back Button Focus.  Just one additional thing.  Once you hit the back button and lock your focus, can you take your finger off of the back button; since the focus will be locked no matter what other settings (aperture, ISO, shutter speeds) you might wish to apply?  If so, how do you reset the the back button for other shots?  Just hit the "*" button?

Based on your samples, I think I'll try it out.

Thanks

Bob

Hi Bob,

I'm not Derek, but yes, you are correct. Once you have acquired focus (lock), you can let go of the back-button. Take as many shots as you like. If you need to refocus, simply press the back-button again and then you can let go. If you are using an STM lens, you can also manually focus this way. It's called full-time manual focus override. You can manually focus even when the lens is set to AF.

When using AI Servo to continuously focus, you need to hold it down. It comes in handy when using AI Servo because you can track (focus) a bird in flight with the back-button, and take multiple shots using the shutter (burst). As long as you hold down the back-button, it will continuously refocus and you can then keep the shutter button down to take bursts of in-focus shots. Of course, your mileage will vary with respect to the in-focus part.

Regards,

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TC63
TC63 Regular Member • Posts: 188
Re: What is Back Button Focus all about?

Here's the YT video in case you are wondering. Since I've started using BBF I won't go back, just my 2 cents

Back button Focusing video

WilbaW
WilbaW Forum Pro • Posts: 11,562
Re: What is Back Button Focus all about?

BobT wrote:

Once you hit the back button and lock your focus, can you take your finger off of the back button; since the focus will be locked no matter what other settings (aperture, ISO, shutter speeds) you might wish to apply?

Correct. Wherever the focus was when you let go of the button, that's where it stays until you press the button again (regardless of AF mode).

If so, how do you reset the the back button for other shots? Just hit the "*" button?

Do you mean, how do you refocus? Press the button again. It's as if you've taken the switch that turns on autofocus from under the shutter button and put it somewhere else.

Based on your samples, I think I'll try it out.

That's what you need to do now. 

But don't try to get it right, just set your up camera that way in Servo and wander around using it like you normally would. If you press and release when the focus is steady that's exactly what One-shot does, and if you hold it down that's exactly what Servo does, so switching between those modes is about whether you hold down the button rather than deliberately setting the "AF operation" mode.

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Hank3152
Hank3152 Forum Pro • Posts: 13,499
Steps to acquire BBF on the T2i

Found this link which may be of help. It gives the procedure to set up your custom functions on the T2i to acquire BBF. It starts near the second photo about 7 paragraphs down..........

T2i BBF

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Regards,
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