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07-20-2009, 02:33 PM   #1
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K10 AF focus wrong - what about MF?

I have recently upgraded from a K100D to a used K10D, and found the K10 AF was out. I corrected this by +100 using a Debug program I downloaded from the web, for v 1.3 firmware. Works a treat for AF.

However, I have 2 MF lenses, a Pentax 50/2 and a Kiron 28/2 which I can no longer use. If I focus correctly in the viewfinder, the results show backfocus every time.

Is there any tricks out there for overcoming this problem, other than stopping down or guessing at a compensation? Stopping down rather defeats the object of having these fast lenses as far as I am concerned. Suggestions gratefully received.

07-20-2009, 03:34 PM   #2
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I don't have any suggestions, but out of interest, what happens if you manual focus with the AF lenses?
07-20-2009, 03:53 PM   #3
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QuoteOriginally posted by Mighty Moose Quote
I have recently upgraded from a K100D to a used K10D, and found the K10 AF was out. I corrected this by +100 using a Debug program I downloaded from the web, for v 1.3 firmware. Works a treat for AF.

However, I have 2 MF lenses, a Pentax 50/2 and a Kiron 28/2 which I can no longer use. If I focus correctly in the viewfinder, the results show backfocus every time.

Is there any tricks out there for overcoming this problem, other than stopping down or guessing at a compensation? Stopping down rather defeats the object of having these fast lenses as far as I am concerned. Suggestions gratefully received.
This does not make sense. if I remember correctly the AF sensor is behind the mirror, and any "debug" setting you apply cannot change the relationship between the cameras actual sensor and the focus screen ?
07-20-2009, 05:00 PM   #4
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the others are not of the SDM focusing system?

07-20-2009, 05:37 PM   #5
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QuoteOriginally posted by Mighty Moose Quote
However, I have 2 MF lenses, a Pentax 50/2 and a Kiron 28/2 which I can no longer use. If I focus correctly in the viewfinder, the results show backfocus every time.
Just curious, do you get focus confirmation light in the viewfinder when you use the MF lens? I did have a back focus problem before my K10D was re-adjusted last time by Pentax support/repair (problem is gone now); I don't remember having any issues with MF (using MF lens) after I adjusted that with the debug menu.
07-20-2009, 06:25 PM   #6
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Another thing to check would be the diopter. Not to insult your camera skills or anything but the diopter can get knocked out, making accurate MF impossible, and it is a simple enough fix.

NaCl(it has happened to me more than once)H2O
07-20-2009, 08:53 PM   #7
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Right, there is absolutely no way any menu setting has any effect whatsoever on manual focus. It's possible your focus screen is misalignedm but it's actually much more likely you are being bitten by the fac thtta DOF in the viewfinder is artifically large. When using f2.8 or faster lenses, the viewfinder will always show more DOF than will be present in the picture (easily verified by shooting some print at an angle and noting how many lines appear to be in focus). So you have to get used to the idea there will be things that appear in focus in the viewfinder but aren't in the picture. With practice, it's possible to learn to work with this and anticipate which objects will *really* be in focus.
07-22-2009, 02:08 PM   #8
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AF OOF when in MF mode

Thanks folks.

It's interesting what you say about DOF being artificially small. That isnt going to help this effect. I get the problem with AF lenses in MF mode too. I'm pretty sure now its the focus screen being ever so slightly out, and theres nothing much I can do other than place some spacers of some sort against the screen. There was a weird U shaped spacer for the K100d which seemed to serve no purpose other than it had to be there for the focus to be right.

One would think that if Pentax can shake the sensor up, down and around for image stability, they could extend this to allow its horizontal distance to lens mount to be calibrated to exactly match the distance to screen. I can undertstand that such a movement would be of absolutely no benefit for image stability but if it fixed this kind of issue for MF it would be cheaper to do than improving their manufacturing tolerances.

07-22-2009, 04:48 PM   #9
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QuoteOriginally posted by Mighty Moose Quote
It's interesting what you say about DOF being artificially small. That isnt going to help this effect.
No it doesn't. But it often *explains* it. In other words, it is absolutely 100% normal and completely unavoidable that there will be things that appear to be in focus in the viewfinder but will not be in focus in the actual image. this is not the result of a misaligned focus screen or an other camera defect - it's just a fact of life. However, if you see the converse - something in focus in the image itself than you can verify was *not* in focus in the viewfinder (and you'll need a tripod for that, so you can check the viewfinder after examingin the picture and expect it to be same as it was before taking the picture), then that is indeed a problem that could be due to a misaligned focus screne - the shim might be too thick or too thin.

QuoteQuote:
One would think that if Pentax can shake the sensor up, down and around for image stability, they could extend this to allow its horizontal distance to lens mount to be calibrated to exactly match the distance to screen.
Interesting concept! It would have to be a hand adjustment, but you're right - it should be possible *if* the stabilization system allow for that type of movement. I'm not sure it actually does, except perhaps in the K7.
07-22-2009, 08:24 PM   #10
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maybe you can adjust the diopter, so manual focus will be more precise.
Should not influence AF.
(Don't know if the K100 had this option)
07-23-2009, 02:34 AM   #11
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QuoteOriginally posted by Marc Sabatella Quote
Right, there is absolutely no way any menu setting has any effect whatsoever on manual focus. It's possible your focus screen is misalignedm but it's actually much more likely you are being bitten by the fac thtta DOF in the viewfinder is artifically large. When using f2.8 or faster lenses, the viewfinder will always show more DOF than will be present in the picture (easily verified by shooting some print at an angle and noting how many lines appear to be in focus). So you have to get used to the idea there will be things that appear in focus in the viewfinder but aren't in the picture. With practice, it's possible to learn to work with this and anticipate which objects will *really* be in focus.
Sorry to threadjack, but am I correct in my understanding that the non-coated aftermarket screens don't have this problem?
07-24-2009, 11:22 AM   #12
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QuoteOriginally posted by Steve Beswick Quote
Sorry to threadjack, but am I correct in my understanding that the non-coated aftermarket screens don't have this problem?
I don't know if it's been definitely established that is the case for *all* aftermarket screens, but my understanding is that the Katzeye screen doesn't have the problem. Although even then I'm not sure if it really *eliminates* the problem or merely *sidesteps* it - anything that the split screen region shows to be in focus really will be, which is all you'd normally care about, but how accurate it is with respect to DOF at wide apertures outside the split screen area I have no idea.
07-24-2009, 07:45 PM   #13
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I have the same problem. I purchased my K10D a couple years ago and I've always had an unacceptly large number of slightly out of focus shots across all my lenses, but I always assumed it was me as this was my first camera plus I've got shaky hands.

Last week I finally bought a good lens, the Sigma 18-50 F2.8 EX DC Macro, and found it to consistantly produce horribly out of focus shots wide open. I found the focus charts, printed them, and tested the camera and found it to be backfocusing very badly. I adjusted it using the russian debug program and now I get dead on focus across all my lenses, the sigma, my A50 1:1.7, my low end tamrons, on the majority of my shots. Whew! Right! Nope.

Now, when the camera says the scene is in focus - and the captured image does turn out to be focused properly - what I see in the viewfinder is distinctly blurry. There's no room for mistaking it. Whether I'm focusing on a flat object directly in front of me or a treeline 200 feet across an open field, my viewfinder image is off kilter with the camera. If I see it sharp, the camera won't lock and produces a blurred image. If the camera says focus is locked and the pic confirms I see a blurred scene.

Adjusting the diopter has no effect but to make the blurring worse. Donning my glasses, which I just got and never wear, has no effect either (even adjusting the diopter with them on).

I've since put my three best lenses on the camera, enabled the debug mode, and taken both very near and far shots at every 20microns of adjustment from zero to 240. The best all around focus is where I orginally set the camera at +140.

I'm debating what can or should be done. It's hard to trust the camera when what I see is so blurry, but worse, for those instances where the camera can't lock or where I want to manual focus, I now know it's a blurry crap shoot to try.

At least I know why so many of my old shots turned out so bad though.
07-24-2009, 11:29 PM   #14
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@KyPainter: As discussed above, the K10d's focusing screen uses metal shims to adjust where it shows a scene as being in focus compared to when the image is actually in focus on the camera's sensor. If you are somewhat handy mechanically and can work with fine tools you should be able to order shims from Pentax USA and try different thicknesses until you get the right one to bring the viewfinder into focus at the right point. I can't recall off the top of my head whether you use thicker or thinner shims than the stock one to correct for back focus but there are discussions about it here on the forum.

I have a Katzeye screen in my K10d and the ground glass area around the prism does show a more accurate depth of field for fast lenses. In my case the screen also helped diagnose a slight back focus issue when using manual lenses but I haven't picked up the shims to fix it yet.
07-25-2009, 05:53 AM   #15
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Thanks, I searched the forum and found a few threads. I wish ordering those shims were easier though, I'd pay more just for the convenience of being able to order them online. If I read correctly I need a thinner shim since I have a backfocus issue.

I tried removing the existing shim completely, just as a test for how things changed, and put it back with no problems (except for a few more dust motes on the screen, but I'll clean them later). Interestingly enough, after I put the shim back there's slightly less of a misfocus than there was before, so maybe the shim or my focus screen wasn't seated properly to begin with.
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