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04-21-2008, 08:39 PM   #1
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Back button Focus

I was reading on another site (I think Canon, sorry) and there was a thread discussing the virtues of using a technique called 'back button focus.' Basically, one removes the responsibility of AF from the shutter release. The back of the camera's AF button then becomes the primary way to AF. This is set up through the Custom menu. I am not sure it is much different than using the shutter release and holding down half-way.

Anyone use this technique? Thoughts?

mark

04-21-2008, 08:47 PM   #2
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I'm sure PDL will jump in. He'd make it impossible to use the Shutter button for focus. Me? I use both. Frankly I find holding and locking the focus with the shutter button, then recomposing the shot works for me much of the time. Especially if things are moving quickly.

My use is more specialized due to being almost totally blind in the right eye and my face covers most of the rear panel. Using the AF button is not very handy. I'm happy the option is there.

Both methods work well and it's really what you are used to.
04-21-2008, 09:06 PM   #3
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At times I will use the back button to AF. Commonly when wearing gloves (it is still cool here) I can inadvertently press the shutter button and take a shot when I just want to focus. In these cases I simply use the back AF button without disabling the AF on half press in the menus.

In other, more rare, cases, I will disable the half press AF and use the AF button solely to focus. One very common use is in cases where the AF is easily fooled, but I want to leave the AF enabled. Once it gets focus with the AF button, I can refocus to my heart's content without the camera giving me the no-go signal.
04-21-2008, 10:37 PM   #4
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I use it as a work around for some action shots, since the Pentax auto-focus speed isn't that hot.

I set the OK button to pre-focus on a spot where my subject is likely to pass through. At the right moment, I just squeeze the shutter button - Zero focus delay.

I managed to capture a 180 mph racing car that way.

04-22-2008, 12:11 AM   #5
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After using manual focus lenses a lot I got used to the focus being set where I left it. So it actually got annoying when the auto focus lens always wanted to change the focus before every shot. But with the AF on the back button it only refocuses when I want it to.
04-22-2008, 03:15 AM   #6
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I'm K100D user, and i prefer to have focus on OK button. It makes it easier to focus recompose and only thing that will engage at pressing shutter half way will be metering an SR. I like it better that way. And when I use remoter wire the camera won't start focusing when I don't need it to anymore since my eye is off the VF. My fiance is using our second K100D body and she prefers to have AF coupled with shutter....
04-22-2008, 02:02 PM   #7
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I'm a convert to using the back button. I find it easier to use than to holdown the shutter button halfway and then recompose. There are some other good things about it; for instance you can set your camera to AF-C and press and release the back button to achieve a single auto-focus or hold it down and get continuous auto-focus. It can also be used in combination with the "AE lock with AF lock" and "Set AE point to AF point" options in the menu. Remember, the only time the focus is "locked" is when the back button is pressed and the green focus indicator is on in the viewfinder. If the back button is not pressed, the camera does not know what it is focused on.
04-22-2008, 05:18 PM   #8
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I turn off the shutter button half-press focus and use the rear AF button when shooting sports. The good thing is that you can then hold the shutter button half down to activate the SR without changing the focus. Even better, when we can get the SR permanently on through a firmware upgrade (hint hint) I won't even have to half press!

04-22-2008, 11:55 PM   #9
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QuoteOriginally posted by Peter Zack Quote
I'm sure PDL will jump in. He'd make it impossible to use the Shutter button for focus.
Actually, no - I would change the default to the AF button however and publish in the front of the manual how to set the shutter button to run the AF. AF coupled to the shutter button just speaks P&S to me - it disconnects me from the process. Your mileage will differ, do what you have to do.

QuoteOriginally posted by Peter Zack Quote
Me? I use both. Frankly I find holding and locking the focus with the shutter button, then recomposing the shot works for me much of the time. Especially if things are moving quickly.

My use is more specialized due to being almost totally blind in the right eye and my face covers most of the rear panel. Using the AF button is not very handy. I'm happy the option is there.

Both methods work well and it's really what you are used to.
My emphasis - I agree in full.

QuoteOriginally posted by kittykat46 Quote
snip
I set the OK button to pre-focus on a spot where my subject is likely to pass through. At the right moment, I just squeeze the shutter button - Zero focus delay.

I managed to capture a 180 mph racing car that way.
Ah - just like the good old days - before SLR's were machine guns. It also helps to know a little about the sport, so you can pick your spots.

QuoteOriginally posted by Gimbal Quote
After using manual focus lenses a lot I got used to the focus being set where I left it. So it actually got annoying when the auto focus lens always wanted to change the focus before every shot. But with the AF on the back button it only refocuses when I want it to.
On my one and only manual lens - I hold the AF button down and twist the barrel until the green hexagon is lit. See the comment from kittykat46, that point is in focus - hit the green button to get the exposure and blast away - and the camera does not hunt between shots.

Now here is another situation - you are shooting a group of people. With the shutter button being tied to AF; you compose the image, take an picture - a twit in the front row stands up and the reaction of the other people in the group is to smack (gently of course) the twit back down. While you are trying to get the shot - AF is grinding away trying to lock on all those hands. By the time AF locks the twit is seated again.

With the AF button - more or less locking the focus - when the twit stands - you push the shutter ------ and ------ wait for it ---- you get multiple images just as fast as you can push the shutter. You get the hands, the expressions the messed up hair the forced smiles. Just because you took control - what a concept.

I know this is a little extreme and really not all that likely, but if your paycheck is tied to getting the off hand shot - why depend on the camera to make the correct decision?

QuoteOriginally posted by Arpe Quote
I turn off the shutter button half-press focus and use the rear AF button when shooting sports. The good thing is that you can then hold the shutter button half down to activate the SR without changing the focus. Even better, when we can get the SR permanently on through a firmware upgrade (hint hint) I won't even have to half press!
I have spoken about sports before - I just agree with what you say.

The idea is that with the ability to couple/de-couple AF/auto ISO/auto f-stop/auto shutter speed with modern cameras - it is the photographer who makes the choice. I realize and expect my cameras to shoot at least 95% of all images correctly (exposure/focus) when in full auto - we all should expect that with any DSLR of any brand. For me - I am trying to live in that last 5% and in order to do that - I have to take control/responsibility. Learning how to use the various controls to achieve what you want is nothing more than craftsmanship. Blasting away at high fps in full auto is - please excuse my high handed opinion - a total waste. I applaud efforts to move away from idiot-proofed cameras - some of us idiots like to push the boundaries.

The Elitist - formerly known as PDL
04-23-2008, 02:00 PM   #10
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QuoteOriginally posted by Gimbal Quote
After using manual focus lenses a lot I got used to the focus being set where I left it. So it actually got annoying when the auto focus lens always wanted to change the focus before every shot. But with the AF on the back button it only refocuses when I want it to.
The best part about using the OK button for focusing is that with M lenses, you can still take a picture if you don't have focus lock.

I actually leave the camera in AF mode and use the OK to confirm focus and shoot away. It worked great when I was shooting a hockey game, and I prefocused on a section of ice and when the players came in, I snapped away.
04-23-2008, 02:13 PM   #11
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QuoteOriginally posted by alohadave Quote
The best part about using the OK button for focusing is that with M lenses, you can still take a picture if you don't have focus lock.

I actually leave the camera in AF mode and use the OK to confirm focus and shoot away. It worked great when I was shooting a hockey game, and I prefocused on a section of ice and when the players came in, I snapped away.
You can do the same thing in af-c mode if you don't want back button focus though. I sort of like the hold down the button and turn the focus ring until it takes a picture method.
04-23-2008, 04:31 PM   #12
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I leave the focus on the shutter button and the rear AF to cancel. That way, I can focus with the shutter but, if I switch to AF-C, when I hold the shutter half way, it will follow focus but it will "freeze" the focus wherever it is at the touch of the rear AF button. Best of both world, since you don't have to go in menus to change anything. I guess it's different strokes for different folks!
04-23-2008, 05:53 PM   #13
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I'm a back button focusser as well.

I dont like to have any of my buttons doing two things at once.
I want to open the shutter when i hit the button....and i dont want to wait for the focus. focus is part of the composition, the camera doesn no thinking for me.
8)
04-24-2008, 07:45 AM   #14
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With my K10D, I used to go back and forth as to using the shutter button and the rear-AF button, but after getting my KatzEye focus screen I almost always have AF disconnected from the shutter and use only the rear button for AF. The AF on my K10D is a 50-50 chance, so I've been using manual focus much more since getting the KatzEye. I hit the AF button if I want AF, otherwise I leave the camera in AF mode and use the quick-shift focusing ability on the Pentax lenses to MF.
10-24-2014, 01:33 PM   #15
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I am a newbie and really struggling to understand- can someone explain how to program a Pentax camera to do Back Button Focus? I have the K-5ii.
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