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03-07-2015, 11:54 AM   #1
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AF-C gives up

I was at a shoot recently with my new K-3, taking pics of speedskating and I noticed it seemed to give up trying to maintain focus after a few seconds of tracking the skaters, especially as they neared me. The only way to reacquire focus was releasing the button and pressing again.

I tried out AF-C at home and it is doing the same thing with all my lenses, both Pentax and non-Pentax. I've tried different settings related to FPS priority, focus priority etc, and it happens everywhere, especially when it hits a non contrasty subject and has difficulty focussing; it then seems to give up..

Am I missing something? Is this a limitation of Pentax AF-C? Is there a repair? I have the latest firmware installed.

03-07-2015, 12:05 PM   #2
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Setting the camera to AF-2 (Button customisation)
Then you will find the AF on your thumb, and not on your trigger.

Also, only use the focuspoint in center.
03-07-2015, 12:28 PM   #3
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QuoteOriginally posted by Runegutt123 Quote

Also, only use the focuspoint in center.
While that may be good advise for a K-3 it is not for tracking in general so much. With an array of focus points that can be assigned a priority, you should, if all goes well, get more in focus of a moving object that may be hard to track. With a single point, tracking and shooting at max FPS, the first time the single point is off the subject or happens to be on a spot that has poor contrast for focusing you can miss the shot.

With an array of focus points under the same situation you have other points to pick up focus if the center goes off the subject or falls on a no contrast part of the subject or scene. This would increase your chances of focus. And ideally your camera should let you tell the array how to behave. For example, give the array outside the center point priority to the nearest or furthest in its field or average the results of all.

Last edited by tuco; 03-07-2015 at 12:33 PM.
03-07-2015, 12:28 PM   #4
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QuoteOriginally posted by Runegutt123 Quote
Setting the camera to AF-2 (Button customisation)
Then you will find the AF on your thumb, and not on your trigger.

Also, only use the focuspoint in center.
No go. It still gives up, especially if something is too close to the focus range, it still doesn't want to refocus on something else when recomposing. Not consistently, but unreliably so.

---------- Post added 03-07-2015 at 01:31 PM ----------

QuoteOriginally posted by tuco Quote
While that may be good advise for a K-3 it is not for tracking in general so much. With an array of focus points that can be assigned a priority, you should, if all goes well, get more in focus of a moving object that may be hard to track. With a single point, tracking and shooting at max FPS, the first time the single point is off the subject or happens to be on a spot that has poor contrast for focusing you can miss the shot.

With an array of focus points under the same situation you have other points to pick up focus if the center goes off the subject or falls on a no contrast part of the subject or scene. This would increase your chances of focus. And ideally you can tell the array how to behave. For example, the array outside the center point will give priority to the nearest, furthest or average the results of all.
I have also tried Centre point expanded, as well as auto 9 point. Same results.

03-07-2015, 12:36 PM   #5
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So it's still the same as with K-5 then? Both my K-5 do the same at times, especially with slower focusing lenses. If they lose focus by too much they may start searching in a too small range to reacquire it and soon thereafter give up.
03-07-2015, 01:15 PM   #6
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I have experienced similar results, it tracks fantastically for a few seconds using expanded center point. After those seconds, the focusing stops and I have to do it again. That said, I don't find it to be a big deal at all. If I pay attention, the tracking re-engages seamlessly. If I lose focus, I lost it due to not being able to follow the subject (fast flying birds - user skill issue here).

I prefer using AF2, I'm still experimenting between AF hold low and off.
03-07-2015, 01:18 PM   #7
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QuoteOriginally posted by CNunez Quote
I have experienced similar results, it tracks fantastically for a few seconds using expanded center point. After those seconds, the focusing stops and I have to do it again. That said, I don't find it to be a big deal at all. If I pay attention, the tracking re-engages seamlessly. If I lose focus, I lost it due to not being able to follow the subject (fast flying birds - user skill issue here).

I prefer using AF2, I'm still experimenting between AF hold low and off.
In my case I was able to consistently track the skaters, but the focus just gave up. I had to reacquire focus. When things are happening quickly, you can lose the shot.
03-07-2015, 01:36 PM   #8
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Yeah I agree on that part. Have you tried measuring for how long it tracks?

03-07-2015, 01:48 PM   #9
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QuoteOriginally posted by CNunez Quote
Yeah I agree on that part. Have you tried measuring for how long it tracks?
It is inconsistent. Although I found with the speedskaters, as soon as they came out of the corner of the oval towards me, that is where the focus gave up. Pressing the button again reacquired focus.
03-07-2015, 02:06 PM - 1 Like   #10
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May Not Be Applicable, Just Mentioning

QuoteOriginally posted by gebco Quote
I was at a shoot recently with my new K-3, taking pics of speedskating and I noticed it seemed to give up trying to maintain focus after a few seconds of tracking the skaters, especially as they neared me. The only way to reacquire focus was releasing the button and pressing again.

I tried out AF-C at home and it is doing the same thing with all my lenses, both Pentax and non-Pentax. I've tried different settings related to FPS priority, focus priority etc, and it happens everywhere, especially when it hits a non contrasty subject and has difficulty focussing; it then seems to give up..

Am I missing something? Is this a limitation of Pentax AF-C? Is there a repair? I have the latest firmware installed.



This may not in your case be applicable, but when I do birding (flying and perching) with my K5-IIS I use center AF and center Metering. Also, if I am trying to pick up something that has any other objects around it, like a bird in a tree surrounded by branches, the center AF setting seems to pick up what I actually point at instead of adjusting itself to the surrounding objects. I use continuous focus and TAV mode most of the time when I shoot outdoors/wildlife. Pressing the button again from time to time to achieve focus is also something that I have done.

Last edited by C_Jones; 03-07-2015 at 02:09 PM. Reason: Edit
03-07-2015, 02:50 PM   #11
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QuoteOriginally posted by gebco Quote

I have also tried Centre point expanded, as well as auto 9 point. Same results.
I see. But I think you'd get the results I described with an array and a focus system capable of what I described.
03-08-2015, 01:58 AM   #12
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In my opinion tracking with a single focus point only is incredibly hard if your subject is moving fast.

There's a difference between trying to focus on a bird sitting in between some branches and one in full flight. Of course multiple points will pick the branches, that's to be expected. You would never use multiple points in that situation anyway.

The question in this thread, is why the camera stops focus confirming after a while of tracking.

It could be the camera has decided that the subject is locked on and no further action is required, maybe the lens is not the best for tracking, or maybe something third.
03-08-2015, 08:25 AM   #13
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QuoteOriginally posted by CNunez Quote
... Of course multiple points will pick the branches, that's to be expected. You would never use multiple points in that situation anyway.
In my case I would. I use multiple points. The center has priority on my camera. If it can't get focus the others pick it up and I usually have them set to give priority to the nearest thing.

Last edited by tuco; 03-08-2015 at 08:31 AM.
03-12-2015, 06:07 PM   #14
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QuoteOriginally posted by CNunez Quote
I prefer using AF2, I'm still experimenting between AF hold low and off.
I know this customization has many avid admirers here, but I don't understand the preference. The AF1 setting gives you back-button AF, and AF when you press the shutter. Given that I learned ages ago to press the shutter gently rather than with a quick jerk, I don't understand why turning off shutter half-press AF makes sense. You can still use the back button to acquire focus - and the pressing of the shutter button gives you the same effect at the instant before releasing the shutter.

Is it the case that the AF button on its own is somehow more accurate than the half-pressed shutter button? Has anyone tested to confirm that this is so? I'm asking because I don't know, not because I question the use of AF2. Obviously, training yourself to press the AF button every time is a major change in routine that would require practice; literally decades of muscle memory to overcome!
03-12-2015, 06:33 PM   #15
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QuoteOriginally posted by ScooterMaxi Jim Quote
I know this customization has many avid admirers here, but I don't understand the preference. The AF1 setting gives you back-button AF, and AF when you press the shutter. Given that I learned ages ago to press the shutter gently rather than with a quick jerk, I don't understand why turning off shutter half-press AF makes sense. You can still use the back button to acquire focus - and the pressing of the shutter button gives you the same effect at the instant before releasing the shutter.
The advantage (or at least one of them) is for focus-recompose situations. If I am just using the shutter button I have to focus on my target, hold it halfway down, move my camera and then take the shot. There is a risk that a variation in pressure will cause the lens to start hunting again, and likely on the wrong object. Or I may want to focus on a fixed spot using AF, and then wait for the action to come there for certain shots, such as a sporting event. By using the back button as the only way to focus I don't have to worry about losing focus every time I twitch the shutter button.
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