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07-19-2011, 01:42 AM   #1
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back focusing k10d

K10D now focusing just beyond whatever I try to shoot.
I've done sufficient tests with tripods, various angles, relying on my eyes and/or the green hexagon.
I've also tried the debug story but no effect - it's also in manual focusing that the camera back focuses with all lenses.

my question is, do you think reverting to a previous firmware could have any impact on this? I currently have the latest installed.

otherwise it looks like at least 100 to send in for repairs, and given that I'd like to sell it afterwards for around 250 that doesn't sound too great.

welcome any other thoughts on this - cheers!

07-19-2011, 04:48 AM   #2
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K10d and backfocus...

...that's a notorious story here.... It worked out with debug mode for me though. But eventually i ended up selling it and buying k20d where you can set fron/back focus for each lens individualy...... pity that feature was not involved in k10, cause I really liked the camera.
07-19-2011, 06:11 PM   #3
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There is no physical cause that could causefocus problems with both AF and MF. So I'd start by posting some of your test shots so people can see if perhaps there is something else going on. It is notoriously difficult to conduct a good focus test.
07-19-2011, 10:27 PM   #4
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Hi David,

I agree with Marc. Some sample shots to illustrate the problem you are seeing are needed to help sort out this problem as focus issues can notoriously be difficult to diagnose. If you can post shots with Exif intact, there are often clues in that information that can help.

Scott

07-19-2011, 11:39 PM   #5
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it may only be MF problem

I defer to your judgement pentaxians and will do another test and post some pics.

Meanwhile though, I actually only did MF tests with focus charts and a sign farther away. In every case when the subject was in focus and the green hexagon more or less confirmed it then I really only had crisp focus when I focused a slightly beyond what appeared correct.

If it's just a back focus problem in MF does that sound like a physical repair?

will do AF tests today as well & thanks again!
07-20-2011, 11:17 AM   #6
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Ok, yes so in both manual and auto focus the focusing is not correct. is this a physical repair (both estimates I got were around 100 !) or does anyone think firmware downgrade could help or any other suggestions? It's not user error, I did plenty of test shots, these are only some:

back focusing k10d pictures by davidxgreen - Photobucket

the wall I focused on the white blob, the first image of text the focus was on the "s" in "changes"
07-21-2011, 02:24 AM   #7
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exif intact

Hi Marc
"There is no physical cause that could causefocus problems with both AF and MF"
If that's true? Then what does this lead you to think is the problem here?

I can rule out viewfinder error, as the viewfinder corresponds to the green hexagon and the autofocus is equally out.

I am ruling out any mistakes on my part with focusing/testing. It wasn't as "scientific" as some people will suggest but I took loads of shots, then the same shots with a k20d (everything was in focus as it should be). In any event, if y'all could assume my tests are fine and start from there I'd appreciate it.

As far as repairs, I've been quoted about 100 so am hoping to find a different solution.

and exif is intact (right click to download them from the site) but I'd be happy to email any of you the larger files if you PM me an email address.

thanks again!
dave
07-21-2011, 07:20 AM   #8
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I have heard of mirror issues with the K10D that cause focus problems when they get older, like around 50K shots. That would affect both manual and auto focus. The green hex is reading the AF sensor so going by that is not actually manual focusing. Adjust your diopter and then focus using your eyes to fine tune your shot. The quick shift feature on Pentax lenses is for exactly that reason.

07-21-2011, 08:57 AM   #9
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QuoteOriginally posted by davidxgreen Quote
I actually only did MF tests with focus charts and a sign farther away. In every case when the subject was in focus and the green hexagon more or less confirmed it then I really only had crisp focus when I focused a slightly beyond what appeared correct.

If I read your comment correctly here, then it seems that when you try to manually focus, what your eyes see as being in focus is actually off. This is problem #1. This sounds very much like a focus screen shim issue - which is common and I've seen it with 2 of 3 K10D bodies that I have. The effect is that you can't trust your eyes to tell you that a shot is right, whether or not the AF is set. This can be made more difficult with the factory shipped focus screen as it tends to show more wiggle room than your lens may allow - giving a false sense of being in focus.

Problem #2 may be that your AF needs to be adjusted using the debug mode. This is a separate task than the shim exercise.

Both problems can simultaneously exist and when they do it can be a pain to sort out.
07-21-2011, 09:13 AM   #10
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interesting

first of all, reeftool, it is just beyond 50k shots, but the diopter is ok and whether using my eyes plus/minus the green hexagon or AF it's all out of focus.

smigol also, sounds exactly right about the MF and I was going to object to your idea that the AF is a separate issue because I did play around for ages with the debug mode...but only in MF. So I suppose the logical thing now is to go back and play with the debug and see what effect it has on AF (it should, shouldn't it!?!) then it will seem to be the two issues you mention simultaneously.

thanks to both of you. will post what happens after more testing.
07-21-2011, 09:32 AM   #11
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David,

Debug is exclusively for AF adjustment. It won't affect MF at all. Note that the focus confirmation that you get while using MF is a function of the AF system saying that it believes you have the subject in focus.

I suggest nailing down the AF portion first before dealing with the shim issue.

There are other resources online here on the forum regarding best practices for conducting AF testing. Quick points to keep in mind:

* Use a tripod to ensure consistent distance to your subject as you test.
* Confirm critical focus on a large monitor - don't use the camera LCD except as a rough guide. Even at 12x it can be difficult to see.
* Employ consistent lighting. Either conduct the entire test using sunlight or incandescent light. Don't change halfway through. I have found that the K10D is sensitive to the color of the light for AF. Two bodies for me take a setting of +140 for sunlight and +90 for incandescent. Expect a difference and test for it so that you know.
* Use a lens with the widest aperture you can have. The 50mm f1.4 is a classic if you have it.
* Use a working distance of about 2-3 meters.
* Fix the central focus point to ensure the camera is going to the same spot each time.

When you have the AF working for you, then you'll know that if you trigger AF it will be correct whether or not your eyes tell you otherwise.

If you still see that the viewfinder is showing stuff out of focus when the AF is correct, then you have the shim problem. You can order shims directly from Pentax and they're not terribly expensive - about $10 for the whole set (I think it's 6 shims). Once you have them in hand you can replace and test using a variation on the AF test where you try to MF and check for front focus and back focus and swap the shims carefully.
07-21-2011, 10:04 AM   #12
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brilliant!!!

Unbelievable! Thanks so much. With about 80+ in the debug mode, all the lenses in AF are correct (will do a more precise test later but all evidence so far is good). AF finds the right spot but it seems a bit blurry through the viewfinder.

When I manual focus and rely on the hexagon, you're exactly right - through the viewfinder is out of focus but the green hexagon is correct. Each time I slightly adjust the MF to fit what my eyes see then it's out of focus.

very pleased. thanks again. will now go and educate myself about the shims story, never heard of shims...you saved me over 100 so thanks for that (owe you a beer if you're ever in london...)
07-21-2011, 10:12 AM   #13
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Great that this is working for you!

Once I had the AF working well for me, it was nearly a year before I tackled the shim issue. I knew that I could trust the AF and so I relied in it. Of course, getting focus right for macro was a hassle so I finally did the shims.

You can try using paper shims if you want to play with it. I did that for a while.
07-21-2011, 12:52 PM   #14
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shims and no mechanical skills

this page gives a good explanation about the shims
K-7 shims

- so I won't be trying that on my own as I've got no mechanical aptitude. If there's anyone in london that might help me out with that (e.g. do it for me) I'd appreciate it.

I've written to SRS if they sell the shims and if not will contact pentax.

I suppose the other option is to pay for a sensor clean and have whoever throw in the shim swap for a nominal extra fee...

in any event, its 100% better now so thanks again! by the way smigol, great pics on your sites!
07-21-2011, 01:37 PM   #15
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I have excatly same experience with my K10D as David. And what smigol suggested has exactly worked for me.

For me, I now rely on AF confirmation since I have adjusted AF on my K10D. I realize if I rely on my eye through viewfinder, then my pic will be out of focus (back focus to me too).

I feel (have heard) mirror and mirror box errors are the possible reasons:
1. If mirror gets distorted over time of usage, it won't be square to focus screen and AF sensor. (There's support point beneath only one side, not both sides, of mirror at down position.)
2. If mirror box is not perfect square , it can have focus error from day one.

Above reasons can also cause the notorious tilt image problem many have reported for K10D, which I unfortunately also experienced.

Of course, other reasons might play roles too.

Last edited by hyyz; 07-21-2011 at 01:54 PM.
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