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03-14-2008, 04:03 AM   #1
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K10D Back-focus problem...

I've had my K10D for almost a year now. After getting the 31mm Limited lens, I thought that I had a bad copy of this lens. Not so. I tried my 35mm and another wide lens and found that the point of focus was pretty far behind the target.

At 35mm, wide open, it is noticable. With the 31mm, wide open, it is bad. The reason that I hadn't noticed it sooner, was that in order to see this problem, the lens had to have a narrow DOF to make it obvious. At f/4 or f/5.6 the DOF was masking it.

Another thing that I noticed is that it gets worse, as the lens gets wider. It is fine at 50, bad at 35, really bad at 31, and I thought that I had a bad copy of a 14mm last month and sent it back!! All the time it was my K10D.

I read somewhere that this is a software calibration issue. That the K10D can be calibrated at several focal lengths for autofocus.

I am thankful that I found this out before the warranty ran out! I cannot afford the K20D for a while, but now I know why they added the "lens self-calibration" feature in it. I would bet that this is a "known" issue, and that Pentax has a lot of cameras coming back under warranty for mis-calibration.

I am sending my K10D back on Monday. I purchased a used *isd DL to get me by until the K10D gets back from Colorado.

Does anyone use the *ist DL as a primary or backup? How do you like it?


Sample "back-focus" photo:

The point of focus is on the bird feeder. I have also done the paper test at 45 degrees. This photo isn't an anomaly.

03-14-2008, 04:08 AM   #2
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I use a DS as a backup. Nice small and light weight package. The 6 MP sensor being a mature design, does a really good job. The DL only has 3 focus points, and a very small buffer, which might get a bit frustrating if you are used to multiple rapid fire shots.
03-14-2008, 04:13 AM   #3
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QuoteOriginally posted by roscot Quote
I use a DS as a backup. Nice small and light weight package. The 6 MP sensor being a mature design, does a really good job. The DL only has 3 focus points, and a very small buffer, which might get a bit frustrating if you are used to multiple rapid fire shots.
Thanks Roscot! I read about the slimmed-down features on the DL and that shouldn't bother me.

I am more concerned about IQ and whether it has issues with back-focus too!
03-14-2008, 06:00 AM   #4
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QuoteOriginally posted by TomInJax Quote
Thanks Roscot! I read about the slimmed-down features on the DL and that shouldn't bother me. I am more concerned about IQ and whether it has issues with back-focus too!
The DL is a 6MP model and the image quality is the identical to all other 6MP models if you shoot RAW. If you prefer jpeg, pick K100D or K110D. The only con with the DL is that the 3 RAW buffer is small, or should I say tiny.

Any Pentax DSLRs can have BF/FF because it is a QC issue and much depends on your luck. If the factory workers did their jobs every one of them should be as accurate as they should be. As to the tests that you have done, just be aware that Pentax DSLRs have wide AF sensors which might cover a much bigger area than you think. Together with less than precisely aligned AF module (against the focus screen), the camera might not be seeing what you think it sees. This design also has the tendency to be attracted by the high contrast background, just like the shot you have shown.

03-14-2008, 08:21 AM   #5
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QuoteOriginally posted by wlachan Quote
This design also has the tendency to be attracted by the high contrast background, just like the shot you have shown.
Thanks Alan,

I had considered the issue with the focus sensors, and decided to do the more lab-like paper focus test at 45 degrees using the Focus test chart by Tim Jackson to verify what I found.

I also tried selecting different focus sensors to see if there was a difference (no). I tried focusing on different parts of the bird feeder, the brass top and bottom caps, the black bracket, the support pole, etc. to see if there was a "good" focus. None were satisfactory.

I used another target in my yard too. We have a small travel trailer parked in our back yard. I tried to focus on several high contrast areas on the trailer: the large brand lettering, a corner, window edges, etc. and found that from about 40 feet away, the point of focus was about 20 feet behind my target. (I looked to the side of the trailer and the trees at the rear of the trailer were in sharp focus.)

So, I got a "Hangover Monday" calibration job when my camera was made. Now because Pentax didn't do their QA on this camera, I have to pay to ship it back to them, thankfully - in warranty!

I used to think that if you ever purchased a Pentax camera, the warranty was nice but not necessary. Now I wonder what an extended warranty on a K20D will cost me...
03-14-2008, 09:01 AM   #6
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QuoteOriginally posted by TomInJax Quote
I read somewhere that this is a software calibration issue. That the K10D can be calibrated at several focal lengths for autofocus.
Never heard this before (about the several focal lengths).
Is that true?
Where did you read that?
03-14-2008, 11:49 AM   #7
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QuoteOriginally posted by blende8 Quote
Never heard this before (about the several focal lengths).
Is that true?
Where did you read that?
Here is the link:

Re: "K10D can register 4 lenses for AF adjustment": Pentax SLR Talk Forum: Digital Photography Review

You were on this thread!
03-14-2008, 12:03 PM   #8
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I sent mine in this week for same re-calibration issue. No experience with the DL, but I do have my original DS (sold it to my bro) back in my hands until then. Love the smallness of this little marvel; especially given how "bulky" my K10 has become with grip attached.

03-14-2008, 12:53 PM   #9
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I'm pretty happy with my DL. I usually shoot in JPEG, and when I have shot in RAW and adjusted from there I think it has been better. I am saving for a K10, but will keep it as a backup (although my wife informs me that when I buy another the DL is hers...)
03-14-2008, 05:22 PM   #10
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I have a samsung gx-1l which I believe to be the same as a dl. I love it. In my opinion its better than a k10d. Hopefully , that will change when I recieve my k10d back from service repair from pentax. I have a second k10d which I bought on the forums but i'm afraid i will have to have that on adjusted also.
03-14-2008, 09:38 PM   #11
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Is a misaligned focus point indicator (the red rectangle that lights up on the focus screen) the same thing as front/back focus? My K10D with a Katz Eye clearly shows that the focus point indicator is above the center line of the focus screen. However, testing with a focus chart shows that the AF sensor itself seems to be aligned correctly with the center line. Against a focus chart, this causes a front focus problem if I select what I'm focusing on using the lit focus point.
03-14-2008, 09:48 PM   #12
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I'm curious about this myself Tom. I've returned 2 lenses and it might be the camera. When you get it back, I'd like to hear what the result is.
03-15-2008, 01:09 AM   #13
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QuoteOriginally posted by TomInJax Quote
Thanks Roscot! I read about the slimmed-down features on the DL and that shouldn't bother me.

I am more concerned about IQ and whether it has issues with back-focus too!
Hi TomInJax

I use a DL as a backup - actually I gave it to my wife when I bought my K10d (sorry to hear yours is problematic). The DL is slimmed down, but takes great photos - one attached here to view. This was taken as we drove home to Adelaide from a trip to Queensland (about 3000kms) over XMAS 2007, just seemed like to good an opportunity to miss.. Oh yes, I should credit my good wife with this shot as I was driving at the time. Obviously, its the back of a wine tanker driving in front of us.

In the interim, I think the DL will do for you quite well.
Attached Images
 
03-15-2008, 04:52 AM   #14
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Great photo Outlaw! I am looking forward to the DL (If I ever hear from the seller!)
03-19-2008, 01:12 PM   #15
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I got the *ist DL today. Wow! The images are amazing! And yes, it works just fine with the 31 Limited! I have never seen such sharp and clear photos with the 31!! I think that I must have had more wrong with my K10D than the backfocus issue. Well it will come back from Pentax better than new.

I am thinking of selling the K10D when it returns from service, rather than the *ist DL. I like this little camera, and I can get twice as much money for the K10D than the *ist DL.

Anyone need a K10D body? I have a new K20D that will be delivered tomorrow!
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