Canon 7D Back Button Focus Setup

[snerd]

Well, this is embarrassing. I guess I'm a 'tard, because I can't get this set up right. In Menu on the Custom Functions menu, C.Fn IV:1, I cannot find an option to turn off AF on shutter half-press. The BBF is already on just below that, but how do I get it off the shutter? There is no "off" choice on that function! I know, I feel so Miley Cyrus right now. :scratch:

 

[snerd]

I left metering on the shutter button and that seems to have done the trick. It's just weird having metering on both the BBF button "and" the shutter half-press button. Seems it could have been explained far better than what it was.

 

[Big Mike]

It sounds like you figured it out, but yes...there isn't an 'off' setting for AF on the shutter release button, you just set it to something that doesn't include AF. For example, metering and AF lock.

Doesn't the 7D have an "AF-on" button?

 

[BigBazza]

It sounds like you figured it out, but yes...there isn't an 'off' setting for AF on the shutter release button, you just set it to something that doesn't include AF. For example, metering and AF lock.

Doesn't the 7D have an "AF-on" button?

Excuse my total ignorance but why is the BBF a good thing to practise ??

 

[JacaRanda]

It sounds like you figured it out, but yes...there isn't an 'off' setting for AF on the shutter release button, you just set it to something that doesn't include AF. For example, metering and AF lock.

Doesn't the 7D have an "AF-on" button?

Excuse my total ignorance but why is the BBF a good thing to practise ??

3 Reasons Why You Should Switch To Back Button Focus

 

[snerd]

Mike, yes, it has an AF On button. I'm playing around with this setup now and it's weird for sure. But I can see that I am going to like it when It's second nature.

 

[TCampbell]

It sounds like you figured it out, but yes...there isn't an 'off' setting for AF on the shutter release button, you just set it to something that doesn't include AF. For example, metering and AF lock.

Doesn't the 7D have an "AF-on" button?

Excuse my total ignorance but why is the BBF a good thing to practise ??

Back-Button Focus was added to cameras mostly as a result of heavy demand from sports photographers.

Here's the scenario:

Keep in mind that without BBF, your ability to shoot is on the _same_ button used to take an exposure reading and auto-focus. As a sports photographer, you'd put the camera into a "continuous" focus mode because your athlete is on the move and likely getting either nearer or farther. So you flip it into the appropriate mode (Nikon AF-C / Canon AI-Servo).

Now you're watching through the lens and tracking your athlete as they run down the field... and you're waiting for that "decisive moment" (often when an athlete does some key interaction with the ball such as throwing, catch, kicking, blocking, all depending on the sport.)

And as you do this... you're JUST about to shoot... when SUDDENLY, a referee enters the frame. And they're much closer to the camera than your athlete so naturally the camera gravitates to them as the new "focus target". You snap the shot and have a beautiful shot of a game ref... with a blurry player in the background. You think of lots of colorful metaphors which aren't polite to type in this forum to describe your opinion of what just happened to you.

WITH BBF:

Same scenario... only this time the _only_ thing the front shutter button does... is take the shot. It doesn't focus. You get to use your thumb to focus the camera but as it's completely independent, you can hold the BBF while your athlete is moving. As soon as you see a 'hint' of that referees body enter the frame, you take your thumb off the BBF so that the camera _remains_ focused on your athlete... if the athlete keeps moving past the ref, then you can put your thumb back on the BBF to let it resume focus. But even if you had shot when your thumb was not on the BBF, the focus would have remained at the last focus distance and the athlete probably would not have been able to move out of your depth of field -- so you still get a focused shot.

The BBF allows you to control when the focus should or should not change because you can choose when to engage or disengage the focus system independent of the shutter.

Recent and high-end cameras are even more advanced because they have focus tracking to follow action and it may be tunable focus tracking. Canon has a 47 page guide on how to tune the focus system on the 1D-X and 5D III cameras for any given sport or situation -- it's pretty powerful. With such a system, you can tune the camera to ignore periodic distractions passing through the scene... or tune it to rapidly jump to new subjects, it's all up to you.

 

[grafxman]

It sounds like you figured it out, but yes...there isn't an 'off' setting for AF on the shutter release button, you just set it to something that doesn't include AF. For example, metering and AF lock.

Doesn't the 7D have an "AF-on" button?

Excuse my total ignorance but why is the BBF a good thing to practise ??

I shoot a lot of wildlife and I missed a lot of shots before I set my 7D to use back focus only. What would happen is the camera would suddenly focus on something I didn't want it to focus on, usually foliage. I would wind up with limbs and shrubs in perfect focus and the animal would be out of focus. This was happening because when I went to take the shot the camera would refocus. Here's an example of what being able to focus with only the back focus button can accomplish for you:

IMG_0752 | Flickr - Photo Sharing!

Notice how the Great Blue Heron's eye is in focus but the intervening foliage is out of focus. I used the back focus button to focus on the bird's body which is visible then moved the camera to get the rest of the bird. The aperture is wide open for a shallow depth of field. It's the best mod I ever did to a camera.

 

[Gavjenks]

Excuse my total ignorance but why is the BBF a good thing to practise ??

It can be summed up simply as the fact that it makes sense to have two different things (focus and shutter) controlled by two different buttons, for more control. Since you might not always want one to happen right before the other.

 

[Big Mike]

I think it's been adequately explained, but I'll add my two cents anyway

By taking AF away from the shutter release button and putting it onto another button, it allows you to separate those two functions. In the regular/default setting, the lens will auto focus when you half press the button (unless you turn it off completely)...and so every time you do a full press to take the photo, you are activating the AF.
That isn't a problem, especially if you know how to use the different focus modes (mainly; still subject mode and moving subject mode). In other words, if you want to lock the focus on a subject (distance) you use the still subject mode and if you want to constantly refocus on a (likely moving) subject, you use the continuous focus mode (AF-C or AI Servo).

But by using the technique of Back-Button-Focus, you can have the best of both those modes. For example, I often have my focus mode set to AI Servo so that I can track moving subjects, but when I want to lock the focus (so that I can focus and recompose, for example), then I simply release the back button, which turns off (locks) the AF.

So simply by pressing or releasing my thumb, I'm locking or unlocking the AF (like One Shot) mode, but when it's held down, it's in AI Servo mode.

The only downfall (which took me a while to figure out) is that when using (or wanting to use) an AF assist light...the AF assist light only works when the camera is in One Shot AF mode.

 

[BigBazza]

Thanks makes sense ......... I can see the benefits ........... clever these chineese hehehe