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10-19-2012, 04:39 AM   #1
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Expanded-area AF - anyone used it?

Has anyone used the Expanded-Area AF [p-103 K-30 manual] feature of the K-30 much? How does it perform?

QuoteQuote:
"When [Expanded Area AF] in [AF Settings] of the [A Rec. Mode 2] menu is enabled, if your subject briefly moves out from the focus point that was selected when the focus mode was set to AF.C (or when [AF.A] was enabled), the camera will continue to focus on your subject based on information from the focus points (back-up focus points) surrounding the selected focus point. The back-up focus points are displayed in pink on the status screen."
Now that the K-5 II/ K-5 IIs manual is out, I note that the K-5 II has exactly the same feature [p-115 of the K-5II manual].

10-20-2012, 02:54 AM - 3 Likes   #2
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I have used it and found it to work reasonably well. I have shot airplanes at an airshow, birds in flight and antique cars in a race. I always set the centre point as the main focus so the surrounding 8 points can take over when the subject moves. I'm not quite sure in what situation one would use any of the other points as the primary one.

I had previously used my K-r in such situations and found it difficult to keep such subjects in focus with continuous AF so instead I would use single AF and then either refocus before each shot if the subject was changing distance quickly (such as approaching or receeding) or else if maintaining reasonably constant distance I would focus once and then not fully release the shutter between each shot so as to prevent refocussing. If I used continuous AF what would happen is that since I could not track perfectly the fast moving birds the focus point would at times fall onto the sky or the trees in the background and would therefore be constantly refocusing between the background and the bird. Of course if I had a steadier hand and could keep the bird dead centre it wouldn't make a difference, but I don't.

The expanded focus on the K-30 seems to help a lot in such situations. As long as you first get the subject centred and then keep it reasonably within the nine focus points it will lock on to the subject very well. With a screw focus lens you can even hear the difference as in the normal mode it will be constanly chattering as it shifts focus between the background and the subject whereas with the expanded area AF you can hardly hear the movement as the focus gradually tracks the subject. With a DC or SDM lens you probably won't notice the difference while shooting but you will of course still see the difference in the photos.

This function is a very welcome addition even if perhaps quite late. This had been one of the few things I was disappointed not to have on the K-r (the other major one being an articulated LCD). Now I am glad it is on the K-30 but I think it has still some way to go before it is comparable to what is available on the other brands. That said, although I have seen some much more capable systems I don't know what price ranges those cameras were.

The main limitation is the small number of focus points that it can switch between. This limits both the areas covered (very near the centre of the view) as well as the ability to keep track when the subject falls between the focus points.
10-20-2012, 12:49 PM   #3
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Lister6520 - Thanks for this! I've been looking at it in the manual, and on the camera - but not seeing what it's designed to do.... That's a nice description of what it's meant to do, how it's meant to do it - and how to use it.

A short play-around - out the kitchen window - now shows - thaaat's what it does - and how....!

Very much appreciated - "adds a function" - to the uses!

Regards, Dave.
10-20-2012, 02:07 PM   #4
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QuoteOriginally posted by lister6520 Quote
I have used it and found it to work reasonably well. I have shot airplanes at an airshow, birds in flight and antique cars in a race. I always set the centre point as the main focus so the surrounding 8 points can take over when the subject moves. I'm not quite sure in what situation one would use any of the other points as the primary one.

I had previously used my K-r in such situations and found it difficult to keep such subjects in focus with continuous AF so instead I would use single AF and then either refocus before each shot if the subject was changing distance quickly (such as approaching or receeding) or else if maintaining reasonably constant distance I would focus once and then not fully release the shutter between each shot so as to prevent refocussing. If I used continuous AF what would happen is that since I could not track perfectly the fast moving birds the focus point would at times fall onto the sky or the trees in the background and would therefore be constantly refocusing between the background and the bird. Of course if I had a steadier hand and could keep the bird dead centre it wouldn't make a difference, but I don't.

The expanded focus on the K-30 seems to help a lot in such situations. As long as you first get the subject centred and then keep it reasonably within the nine focus points it will lock on to the subject very well. With a screw focus lens you can even hear the difference as in the normal mode it will be constanly chattering as it shifts focus between the background and the subject whereas with the expanded area AF you can hardly hear the movement as the focus gradually tracks the subject. With a DC or SDM lens you probably won't notice the difference while shooting but you will of course still see the difference in the photos.

This function is a very welcome addition even if perhaps quite late. This had been one of the few things I was disappointed not to have on the K-r (the other major one being an articulated LCD). Now I am glad it is on the K-30 but I think it has still some way to go before it is comparable to what is available on the other brands. That said, although I have seen some much more capable systems I don't know what price ranges those cameras were.

The main limitation is the small number of focus points that it can switch between. This limits both the areas covered (very near the centre of the view) as well as the ability to keep track when the subject falls between the focus points.
Are you finding this to work using the the OVF (PDAF)? C-AF or S-AF? I know it works in LV if focusing is set to "tracking". Thanks.

10-20-2012, 03:48 PM   #5
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QuoteOriginally posted by lister6520 Quote
I have used it and found it to work reasonably well.
Thanks for the comprehensive description.

I was curious about how this feature differed from normal AF.C continuous tracking. Looks like the feature works OK.

The Pentax manual was very cryptic about what the feature is, and how it works.
10-21-2012, 09:01 AM   #6
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QuoteOriginally posted by IchabodCrane Quote
Are you finding this to work using the the OVF (PDAF)? C-AF or S-AF? I know it works in LV if focusing is set to "tracking". Thanks.
I have only tried it with the OVF - no idea how/if it works in live view as I only ever use live view for stationary subjects.
10-22-2012, 01:41 AM   #7
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Live view also works pretty well, although I find if the subject is extremely fast moving it seems to "give up" after a while.

Used both to reasonable effect on a fishtank full of cichlids yesterday - they don't half move fast! - both the OVF and LV tracking worked as designed, although with the OVF, due to only using the center cross AF points, and being very very close to the subject, its quite hard work to keep them within the tracking area. I suspect its a lot easier when you are a bit further away!

Compared to my K10D the AF is much more capable.
03-06-2013, 09:42 AM   #8
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I used too, it worked great. Though the manual and the menu indicates that it works only when you are in AF.A or AF.C mode, I found it worked only in AF.C mode.

03-06-2013, 09:56 AM   #9
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Why would someone pick 5 point autofocus over 11 point when tracking? Not a hijack, just expanding the question
03-06-2013, 10:05 AM   #10
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Maybe, because it's easier to pick the immediate neighbouring points? However, your question is valid. Anyway, I'm happy with this feature (not meaning I wouldn't be more happy)
03-06-2013, 11:28 AM   #11
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QuoteOriginally posted by slip Quote
Why would someone pick 5 point autofocus over 11 point when tracking? Not a hijack, just expanding the question
My guess is there's less processing involved with 5-point so it will react quicker.
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