AF on button

Joined
Aug 12, 2007
Messages
417
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Glenwood
Trying to google some articles about how to use this button but coming up short. I have played with pushing it as I follow the action, but not certain about what I need to do also.

thanks for any links or help in learning about this technique.
 
Joined
Sep 21, 2010
Messages
300
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Ontario
So basically the way I have it set up (on my D200) is:

- a1: AF-C mode priority: FPS rate
- a6: AF Activation: AF-ON only
- Flip the AF selector on your body to AF-C

I might have missed some custom setting, but I think that's all I needed to get it working.

That should decouple focusing from the shutter release. Instead of relying on shutter release to focus, I can now use the AF-On button as either selective one-time focus by holding and releasing, or as continuous focus by holding it down while tracking an object.

Using this focus method is a little tricky and will probably be confusing until you get accustomed to it. Basically you use two fingers. One is sitting on your shutter release, but you will use that finger only to release the shutter. My thumb is always parked on the AF-On button. When I track an object I want to focus on, I will hold the AF-ON button until it locks on, then I use my index finger to release the shutter. The best part is that I can hold down the AF-ON button and it will continue to focus as soon as the mirror comes down for my next shot. It makes shooting fast action so much easier.
 
Joined
Feb 20, 2011
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3,853
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New Zealand
I've used this method for a few years now, and sometimes I surprise myself at how I can press and release each button independently at different times as needed. definitely worth learning how to use it properly.
 
Joined
Oct 1, 2008
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3,298
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Florida
I use it, but in the end, shoot however you are comfortable. The one advantage of course is that the camera does not try to focus again when you take the picture...or subsequent pictures. Other than that, its pretty much the same as using the sh rel button
 
Joined
Aug 12, 2007
Messages
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Glenwood
VR

I do use VR but not really sure if that even activates at the high shutter speeds. I recall reading as your shutter speeds go up, then the VR capacity goes down. During basketball I was just pushing the AF button down and holding it because it seemed like it made my pictures sharper. Of course, don't know if that was true or not. I am reading through the threads and articles to learn more about it. Either way, just enjoy reading and learning, so it's all good. Plus, the sun is starting to shine and temps are going up, so about out of the gyms for this year!
 
Joined
Aug 7, 2008
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67
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Sacramento, CA
I just started using it when I got my D7000. It took an outing or two but it feels natural now. Give it a shot, especially when using AF-C and shooting sports.
 
Joined
Feb 20, 2011
Messages
3,853
Location
New Zealand
I just noticed something using the AF-on button and single shot with priority set to focus. If you pre-focus on a spot, then shift the camera a bit to reframe, the focus point selected is no longer in focus, so the shutter won't release! oops.

May have to use the focus+shutter priority for those (not that I understand how BOTH can be a priority).
 
Joined
Aug 12, 2007
Messages
417
Location
Glenwood
So, if I set it up properly, should I prefocus or can I just continue to push the AF-On button to keep the focus where I want it, then hit the shutter release when I want to take the shot?
 
Joined
May 5, 2010
Messages
375
Location
Livonia, MI
David Busch's book covers it real well.
"For example, the AF-ON button can be used to lock focus in separately from exposure & taking the picture, & to produce the effect called trap focus in which you pref-focus at certain point, press the shutter release, & D700 doesn't take picture until your subject (say, a horse crossing the finish line) moves into pre-focused position."
With this setting AF-ON only,you don't have to be concerned w/autofocus lag, the camera will snap picture instantly.
I found his book extremely helpful.
 
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Joined
Feb 20, 2011
Messages
3,853
Location
New Zealand
I just thought of using that for trap focus after I posted my one above - so it does work like that. How fast to fire is it? I was taking pictures of dogs jumping stuff, they are fast, need 1/1500 to freeze the big dogs, I was pre-focussing on the obstacle and firing when they jumped. Would trap-focus recognise it's reached focus and fire fast enough?
 
Joined
Aug 12, 2007
Messages
417
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Glenwood
Book

Yes, I have his book and have read it. It is very helpful. But, I am still not clear on the technique. I get if you want to prefocus on an area. But, what if you are following a player, say in soccer or basketball. As you follow them, what is your technique?
 
Joined
Feb 20, 2011
Messages
3,853
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New Zealand
Keep the AF-on button pressed while tracking them, then press the shutter when you want to shoot. Being able to do both independently from each other can take a bit of getting used to.
 
Joined
May 5, 2010
Messages
375
Location
Livonia, MI
They way I have tried was locking on a certain point for focus w/AF-ON held until subject moves in area of focus & then press shutter to activate metering, then fully depress when moving subject enters focal plane. I am only an amateur but I keep on trying?
 

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