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04-28-2010, 07:36 PM   #1
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Just discovered something about K10D focus

I shot off a few pix before and after updating the firmware, and for the first time I realized something specific about the autofocus. This is with single, center auto focusing, which is how I set it 95% of the time. In the dimly lit room (ceiling light on low and laptop are the only light sources. I casually aimed it at the cat lounging on the counter four feet away, next to the phone. Hunt extreme, hunt extreme, settles not in focus. OK, been there before. I aim it literally three inches to its right, same light, on the phone and try. Hunt, in focus. Repeat. Same results. The cat is a solid grey faux Russian Blue, and every time I tried to focus on her body the K10D just wouldn't, but aim it on an object a few inches away under the exact same conditions and it had no trouble focusing. (Haven't checked to see if they're actually accurately in focus, the pix are very dark. I only had the mechanical aspect on my mind).

It really seems like there's something about the complexity of the solid fur texture that camera can't deal with, not the conditions, though probably under better conditions it deals with it better. (I've shot the cat before in good light, but always had her face as the focus point.) Just for the heck of it I tried the same thing with my old Canon P & S A640 and there was NO difference in focus performance in the same exercise.


This may well be something that others already know but it's a new, interesting wrinkle to me. Now I feel more that it's firmware issue than a limitation of the hardware.

A quick search didn't turn up any revealing info. Anyone else have similar experience?

04-28-2010, 07:46 PM   #2
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QuoteOriginally posted by hut234 Quote
I shot off a few pix before and after updating the firmware, and for the first time I realized something specific about the autofocus. This is with single, center auto focusing, which is how I set it 95% of the time. In the dimly lit room (ceiling light on low and laptop are the only light sources. I casually aimed it at the cat lounging on the counter four feet away, next to the phone. Hunt extreme, hunt extreme, settles not in focus. OK, been there before. I aim it literally three inches to its right, same light, on the phone and try. Hunt, in focus. Repeat. Same results. The cat is a solid grey faux Russian Blue, and every time I tried to focus on her body the K10D just wouldn't, but aim it on an object a few inches away under the exact same conditions and it had no trouble focusing. (Haven't checked to see if they're actually accurately in focus, the pix are very dark. I only had the mechanical aspect on my mind).

It really seems like there's something about the complexity of the solid fur texture that camera can't deal with, not the conditions, though probably under better conditions it deals with it better. (I've shot the cat before in good light, but always had her face as the focus point.) Just for the heck of it I tried the same thing with my old Canon P & S A640 and there was NO difference in focus performance in the same exercise.


This may well be something that others already know but it's a new, interesting wrinkle to me. Now I feel more that it's firmware issue than a limitation of the hardware.

A quick search didn't turn up any revealing info. Anyone else have similar experience?
By firmware did you mean the one that was released couple days ago? I'm about to update my K10D to that firmware as well but I guess I'll wait a bit more to get more feedback from those who have done so.

Can you post some pictures of your test?
04-28-2010, 07:46 PM   #3
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Contrast - that's usually what the camera wants. Something with a clear edge between light and dark. Faces definitely work better than featureless patches of fur.
04-28-2010, 09:01 PM   #4
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QuoteOriginally posted by ducdao Quote
By firmware did you mean the one that was released couple days ago? I'm about to update my K10D to that firmware as well but I guess I'll wait a bit more to get more feedback from those who have done so.

Can you post some pictures of your test?

I was really just trying out the mechanical aspect, wasn't thinking about the images. Had it in manual and ignored the shutter and aperture settings, so the pics are very dark, dark enough to not be of use.

I'll do some more controlled tests in the next few days, but my initial impression is that the new firmware had no effect on the autofocus. Didn't seem to cause any harm.

BTW, lens was a Tamron 28-75 2.8 XR Di LD, which I like a lot, both as a performer and for its results.

04-28-2010, 09:08 PM   #5
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Instead on the body of the cat, center your focus point on the 'edges' of the cat. That works for me in such cases
04-28-2010, 09:21 PM   #6
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This is what was so great about split prism screens. They teach you to focus on high contrast areas of the scene. As Marc said, AF needs contrast.
04-29-2010, 06:41 AM   #7
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Interesting post, as my cats are my usual suspects for photos but I usually shoot (and shoo) them outside with plenty of contrast, which I obviously did not even consider being a factor prior to now.

BTW, I think they consider themselves much more substantial than "featureless patches of fur"...
04-29-2010, 06:50 AM   #8
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QuoteOriginally posted by ducdao Quote
By firmware did you mean the one that was released couple days ago? I'm about to update my K10D to that firmware as well but I guess I'll wait a bit more to get more feedback from those who have done so.

Can you post some pictures of your test?
I've done the update on my K10D and K20D with no noticeable problems. Some say they notice an improvement in focusing but since I am happy with what I have I can't say the same.

04-29-2010, 06:57 AM   #9
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Since my cat is mostly black with some white on it (makes the autofocus go crazy), I usually point the focus indicators at her eyes. Does the trick.
04-29-2010, 07:28 AM   #10
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QuoteOriginally posted by hut234 Quote
I shot off a few pix before and after updating the firmware, and for the first time I realized something specific about the autofocus. This is with single, center auto focusing, which is how I set it 95% of the time. In the dimly lit room (ceiling light on low and laptop are the only light sources. I casually aimed it at the cat lounging on the counter four feet away, next to the phone. Hunt extreme, hunt extreme, settles not in focus. OK, been there before. I aim it literally three inches to its right, same light, on the phone and try. Hunt, in focus. Repeat. Same results. The cat is a solid grey faux Russian Blue, and every time I tried to focus on her body the K10D just wouldn't, but aim it on an object a few inches away under the exact same conditions and it had no trouble focusing. ....

This may well be something that others already know but it's a new, interesting wrinkle to me. Now I feel more that it's firmware issue than a limitation of the hardware.

A quick search didn't turn up any revealing info. Anyone else have similar experience?
As Marc already hinted at: contrast is the problem, or the lack of contrast.

A certain contrast level is the well-known prerequisite for any passive AF system to work. If you do not have contrast no passive AF system can work. (Contrary to active AF systems around ultrasonic - the old Polaroid method - or IR emitters).

Your experience is interesting in so far, as it shows, that most people are still not aware of these inherent limitations of AF systems - not the least because the camera makers do not exactly shout out loud about those limitations. But ofcourse it is mentioned also in the camera manuals.

Ben
04-29-2010, 09:16 AM   #11
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Was about to say the same thing; I don't have cats but the ones I've shot I usually use the eyes as they have the most contrast.

QuoteOriginally posted by VF-19 Quote
Since my cat is mostly black with some white on it (makes the autofocus go crazy), I usually point the focus indicators at her eyes. Does the trick.
04-29-2010, 12:48 PM   #12
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QuoteOriginally posted by NRV Shooter Quote
Interesting post, as my cats are my usual suspects for photos but I usually shoot (and shoo) them outside with plenty of contrast, which I obviously did not even consider being a factor prior to now.

BTW, I think they consider themselves much more substantial than "featureless patches of fur"...
In history, many years ago, in Egypt and other places, cats were considered as Gods. They have never forgotten this.
04-29-2010, 02:10 PM   #13
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Perhaps you need the full set ?



( I couldn't resist, no matter how hard I tried. )
04-29-2010, 02:31 PM   #14
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As said, the AF requires contrast and this is just something you have to work around. Try focusing on a blank wall, AF will usually hunt like crazy and then not achieve focus.
04-30-2010, 06:06 PM   #15
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What irks me though is that now that I've used it for three years, my K10D strikes me as one of the weaker autofocus performing DSLRs I've used, and it's usually not a case of directly focusing on a low contrast subject. It's mostly when needing to get shots off in before the chance is lost, especially in compromised conditions. And not even sports or fast action racing by, just normal shoots where the lighting is low and I have to constantly set focus on something other than what I'll be attempting to focus on first. I've been hoping that a firmware update over the years would put it closer to other more responsive cameras in its range that I've used and noticed the difference with. Still like the results of the Pentax when it can handle the conditions, though : )

I was really hoping that the A640 would be just as fooled by the subject but it wasn't.

Part of my frustration with this is that I've been willing, and expecting, for years to move up to an upgraded Pentax, and the K20D just didn't entice me enough. I was assuming that by now a $1,800 "K30D" would appear between that and the 645D, but no such luck : )
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