I've heard other people rave about using the back button for focusing. Does it continue to track the focus point after the button isn't pressed? If nothing else I think that would suck the battery pretty fast and get confused when you point it down or elsewhere.

I'll have to mess with it to see how I like it. I could see missing a number of shots at first.

I've heard other people rave about using the back button for focusing. Does it continue to track the focus point after the button isn't pressed? If nothing else I think that would suck the battery pretty fast and get confused when you point it down or elsewhere.

I'll have to mess with it to see how I like it. I could see missing a number of shots at first.

Nope. No battery drain. Here is how you set it up on a Canon 5D II:
- MENU >> far right Camera icon for Custom Settings
- C.Fn IV: Operation/Other Sutter button / AF-ON button (menu choice 1)
- Nav down to 3: AE lock/Metering + AF Start and activate (it will now be highlighted in blue)
________________________________
- Put camera in IA SERVO mode
- Lens on Auto Focus

NOW...
Look through viewfinder and place the central focus point  on an object to focus on. (assuming that is the one you have set to focus with)
- Press the AF-ON button on the back of camera and central focus mark will flash RED when focus is achieved.
- NOW TAKE YOUR FINGER OFF THE AF-ON BUTTON
- Your focal plain is now set. You can recompose & shoot all day WITHOUT refocusing as long as you or it does not move forward or backward. Sweet

Now lets say things start moving...
- Hold down the AF-ON button and IA SERVO kicks in so you can focus track and fire the subject in focus as long as  you continue to hold the AF-ON button down.

You can do this on all of the high end Canons and Nikons but I only know the setting for the 5D.

Hope this helps.
OX

Yes use it all the time. One big advantage in a static situation is that after focussing once, you can recompose and fire away at will.

So for the money one pays for a high-end camera, wouldn't you think the autofocus button would work this way, instead of having to rig some other part of the camera to do the autofocus's job? 

Also, if you let a friend use your camera, this will drive them batty.

LMAO!!! !!!

Thanks Oxman for the detailed instructions for the 5D Mark II, I'll try it tonight. Hopefully I can use the custom settings on the dial to switch back and forth (my wife uses my camera every now and then).

You are welcome Kingjon. I think you will like it. And perhaps your wife will as well.

thanks ox - this is a very informative post.
I will have to try setting up this arrangement and giving it a try!
cool!
nice to have an educational post once in awhile among all the complainin'

+1

A custom function would work for situations in which you can lock focus but the AI Servo thing is only really useful if you have a lens with a fast AF. I tried it at a horse show and was disappointed. The AF couldn't keep up. I was hoping it would allow me to get more than I would ordinarily get.

Quote from: digitalexpression on June 21, 2012, 12:05

A custom function would work for situations in which you can lock focus but the AI Servo thing is only really useful if you have a lens with a fast AF. I tried it at a horse show and was disappointed. The AF couldn't keep up. I was hoping it would allow me to get more than I would ordinarily get.

I use AI Servo at motocross.  It seems to work very well.  Can't see why it wouldn't keep up with a horse?   I used a single focal point (the center point).  Did you try that?

A "fast AF lens" would seem obvious for sporting events.

 

merely pointing out my experience trying it. Do the motocross bikes come directly at you? That was my problem. The distance between me and the horse closed too fast for the lens to keep up. I always use centre point for focus BTW.

If you're offering to buy me the Canon 70-200 f2.8 L that's awfully nice of you. If not then pointing out a fast AF lens is "obvious" for sporting events is pretty useless information. I do what I can with what I can Afford. I have the Sigma 70-200 f2.8 and it's an excellent lens but the AF is not as fast as the Canon and not fast enough. But thanks for your 2cents now I can put a down payment on a faster lens.

I just focus it using the AF then turn the AF switch on the lens off.

Stays focus at the same focal length all day as well.. and no menu fiddling...

I have just stumbled across this.  Neat.  It seems to be pretty much about composition and very cool. 

As a poster above mentioned a horse show, I am particularly curious, as that is much of what I do.  In the past, the AF has been tied to the shutter.  It does wander a little, but I am usually able to get the horse in focus at the critical moment as the AF seems to be quick enough.  I use a Nikkor 55-200 1:4-5.6.  I know it's not a fast lens, but it has sufficed.  I also have a "nifty 50" that is faster, but I need the zoom.  Can't afford a truly fast zoom lens.

So, will I do better with the back button AF?  I don't fully understand how the tracking is different without having played with it.

all sports photographers are using BB it takes a while to get used to

Well, I'm all over that - I'll have to check to see if there is a show tomorrow so I can check it out.  Thanks!

I do the opposite. I have a back button on my Nikon set up to lock the focus. I find this accomplishes about the same thing with less time keeping the button held down.

How do you handle moving objects this way? This is not a criticism, I am wanting to try this method while shooting great white sharks in a couple of weeks. The trick for me is to choose a custom assignment that my housing can access.

Quote from: landbysea on September 07, 2013, 12:41

I do the opposite. I have a back button on my Nikon set up to lock the focus. I find this accomplishes about the same thing with less time keeping the button held down.

How do you handle moving objects this way? This is not a criticism, I am wanting to try this method while shooting great white sharks in a couple of weeks. The trick for me is to choose a custom assignment that my housing can access.

The shutter button does the focusing so for moving subjects I can just use the shutter button. But if I achieve a focus I want to keep for a few seconds I just jam the button on the lens side of the camera and it locks the focus. It is very natural and comfortable for me to work that way and involves very little movement while maintaining a good grip.
I corrected my original post because it is a button on the front I have set up not a back button.  I tried the method in the OP , but using a back button is awkward. I much prefer how I do it now and it has most of the same advantages, but not that great for using a remote release, where you might want the BB method to maintain a set focus without touching the camera.

Thom Hogan addresses this in this months teaching article.

http://www.bythom.com/

I think if Hogan had his 10,000 hours in that he refers to he would realize that with that method you are not using the thumb grip properly if your thumb is pushing a button and also has to release tension on said button when focus is achieved, risking dropping longlens and camera into said snow if handholding.  My method requires a very short learning curve, leaves the thumb on the thumb grip and achieves the exact same thing as the BB method. He should have mentioned both ways.