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09-16-2014, 02:01 PM   #1
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AF pressed - function without holding the button?

Hi all, I'd place a question concerning the AF button function. (My problem is that the K-3 manual is not too much detailed and I still can't understand all the AF related options...)


If I hold the AF button, the camera stays focused and the shutter release button can be pressed to take the photo (without prior half-pressing of the shutter release button).


Once I release the AF button, the focus lock is gone. However, is there a possibility to change the behavior of the AF button - in such way that the focus keeps being locked (even after releasing of AF) until the photo is taken?


In some situations I'd like to focus, then rearrange the composition (while stil being focused on the same spot) and finally take the photo by single pressing of the shutter release button. And as between the focus and photo shooting may be quite a long interval, I'd like to avoid holding the pushed AF button for such long time.


I know that switching to MF I can achieve the same, but I'd prefer to have this function in AF mode, too...

09-16-2014, 02:03 PM   #2
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Find the option allowing you to change your AF setting to back button AF. That will let you AF with the back button, leaving the shutter button unassociated with focusing.
09-16-2014, 02:17 PM   #3
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What do you mean AF button? By default, AF is set to be shutter half press, but I guess you have changed that (as many of us have) so that the AF only starts with the AF/AE-L button.
If I understand your wishes correctly, you want to focus and recompose, but you want the AF to stay on the same subject.
Here are your options:
-Use AF point select (instead of auto or centre point only), this way you can choose to AF on any of the AF points
-Use AF.C and AF tracking. This is limited, though, since the camera cannot lock focus in a place where no AF points are placed, so you are not much better off than with the AF point selection. The other problem here might be that the camera doesn't lock on the same object that you want it to.
-Live view, because in live view you can AF on any part of the frame. And focus peaking can help as well, at least with fast lenses.

But no, aside from using triggers, remotes, and timers, I don't think there is any way for the camera to AF without you pressing a button. And even with triggers, remotes, and timers, you still have to press something.. Maybe someone else has better ideas
09-16-2014, 02:26 PM   #4
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QuoteOriginally posted by zzeitg Quote
Once I release the AF button, the focus lock is gone.
No it is not. The focus does not change just because you let go of the button. If you have back button (AF button) set to focus and shutter release button set to release shutter only then you focus with the back button, let go of the button and shoot as much as you want. The focus will not change.

If you have the camera in AF.C then as long as you are holding the AF button down then the camera will keep re-focusing even if you or the subject moves, but once you let go the AF button focusing stops at the last focused point.

Edit: Let me rephrase that, the 'lock' is gone but the focus is still the same, the lens has not changed the focus point.

09-16-2014, 02:37 PM   #5
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QuoteQuote:

In some situations I'd like to focus, then rearrange the composition (while stil being focused on the same spot) and finally take the photo by single pressing of the shutter release button. And as between the focus and photo shooting may be quite a long interval, I'd like to avoid holding the pushed AF button for such long time.


.
You have to disable the "Shutter Button Half Press" option to OFF, otherwise, once you move to recompose, when you press the shutter it will focus again....
09-16-2014, 02:41 PM   #6
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jatrax: yeah, change of AF button setting to AF2 did the trick. Thanks!
09-16-2014, 03:31 PM   #7
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Oh, some more theory on focus and recompose.
AF sets focus to a certain distance from the sensor. As long as this distance between sensor and object stays the same, the object will stay in focus. So recomposing by moving camera left and up will not affect focus. But recomposing by twisting the camera sideways will (changing the orientation, tilt). Another problem is that the depth of field is curved (depending on lens, macro lenses have a very flat field).
But I hope the AF button setting solved your problem for good!
09-19-2014, 03:08 PM   #8
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So I've just found out that the "Catch-in Focus" function does not work if the AF button setting is changed to "AF2". Photo is taken immediately, no matter that the object is out of focus... So to use this function AF must be set to "AF1"...










09-19-2014, 03:33 PM   #9
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QuoteOriginally posted by zzeitg Quote
So I've just found out that the "Catch-in Focus" function does not work if the AF button setting is changed to "AF2". Photo is taken immediately, no matter that the object is out of focus... So to use this function AF must be set to "AF1"...
Yep. One of my pet peeves, and no idea why it has to be that way.
10-02-2014, 01:59 PM   #10
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I just stumbled upon this thread, but wish I had last week when I got my new K-3. I had read about the AF-2 setting a few days ago and while out in the field yesterday remembered to change it. Now it works just like I have my K-5 set up and I'm happy about that. Not so happy about the Catch-In-Focus being messed up when using the AF-2 setting. Maybe it can be addressed in a firmware update? Are you guys in R&D reading these posts, hint, hint?
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