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07-21-2021, 03:47 AM   #1
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Pentax K10D partially blurry images

Hi,

I noticed that I sometimes tend to get pictures that are uniformly blurry on one side of the frame with my Pentax K10D. The lens I'm using is the kit zoom lens, SMC PENTAX-DA 1:3.5-5.6 18-55mm AL II.

Test shot 1; 32mm, f/6.3, 1/800s, ISO 200, Shake Reduction OFF. Developed from raw with Chromatic aberration corrected. Sharpness is very good on the right side of the frame, but decreases linearly towards the left side. Right-click -> Show image to view the full-res image.
Test shot - Album on Imgur


Test shot 2; 32mm, f/6.3, 1/800s, ISO 100, Shake Reduction OFF. Developed from raw with Chromatic aberration corrected. The camera was placed on a tripod and positioned exactly perpendicular to the wall. Similarly to the previous one, the sharpness decreases towards the left side of the frame. Right-click -> Show image to view the full-res image.

Test shot - Album on Imgur

Is the lens somehow faulty or the image sensor slightly misaligned? Could sensor misalignment also be the reason why I had to add up to +150 um of AF adjustment in the debug mode to attain any kind of autofocus accuracy? Is there some way to adjust sensor alignment on this camera body?

07-21-2021, 03:52 AM   #2
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There is no way to alter sensor alignement on Pentax bodies as far as I know. That kind of problems is usually lens-related, there must be a decentering of one lens element. How severe it is, however, I cannot judge.

Best bet is to find another lens. Fortunately yours isn't too costly, even if it is of the "better variety" of 18-55.
07-21-2021, 04:03 AM - 1 Like   #3
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QuoteOriginally posted by artrasa Quote
I noticed that I sometimes tend to get pictures that are uniformly blurry on one side of the frame with my Pentax K10D. The lens I'm using is the kit zoom lens, SMC PENTAX-DA 1:3.5-5.6 18-55mm AL II.
It is possible that the lens is at fault and has become de-centred. The only way to test is to put another lens on and test again.

QuoteOriginally posted by artrasa Quote
Is the lens somehow faulty or the image sensor slightly misaligned? Could sensor misalignment also be the reason why I had to add up to +150 um of AF adjustment in the debug mode to attain any kind of autofocus accuracy? Is there some way to adjust sensor alignment on this camera body?
Having to add AF correction is not by itself a fault. The K10D did not have a menu item for autofocus fine adjustment like more modern cameras, but as you have discovered is possible through a software hack.

The first thing I would do is try another lens if you have one.
07-21-2021, 04:22 AM   #4
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Many thanks for your replies. This is the first time I've heard about a lens being de-centred. Unfortunately I don't have any other PK-mount lens at the moment, but I do have 50mm and 135mm M42-mount prime lenses. I will do a similar test with these manual lenses.

07-21-2021, 07:05 AM   #5
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QuoteOriginally posted by artrasa Quote
I don't have any other PK-mount lens at the moment, but I do have 50mm and 135mm M42-mount prime lenses. I will do a similar test with these manual lenses
They will give you your answer just fine
07-21-2021, 01:31 PM   #6
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QuoteOriginally posted by Bertrand3000 Quote
There is no way to alter sensor alignement on Pentax bodies as far as I know. That kind of problems is usually lens-related, there must be a decentering of one lens element. How severe it is, however, I cannot judge.

Best bet is to find another lens. Fortunately yours isn't too costly, even if it is of the "better variety" of 18-55.
Actually every sensor on any Pentax-body can be aligned.
On the K7 it was very easy: Access from underneath, just bottom off.

Sadly that was dropped again with the K5.

For the TO: if you need to find a good zoom not expensive:
Find a DA16-45ED. Great lens for little money and up to the K3 and KP it showed how good it was. But make sure it is a mint sample!
Some heavy used ones wobble badly and then decenter.

Well treated a great lens, one of the very few zooms I use.
07-21-2021, 05:22 PM   #7
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Wait, a software hack??? This has me interested. Is it possible to do a software hack on my old K5 which will maybe allow focus peaking? And, whilst I am at it, can said software hack also allow use of a PLM lens? ps I do know that a 55-300 PLM "works" on my K5, but will be wide open.

07-21-2021, 07:16 PM   #8
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Looks decentered. Another quick decentering test is to photograph a distant object, like a church steeple, framed in each corner, and compare the 4 shots.
07-22-2021, 02:59 AM   #9
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QuoteOriginally posted by photogem Quote
Actually every sensor on any Pentax-body can be aligned.
On the K7 it was very easy: Access from underneath, just bottom off.
And it is not unusual for the K-10D to get it's sensor moved a bit. Thus I second testing with the M42 lenses.
07-22-2021, 09:33 AM   #10
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Not to forget:
PK_Tether and PKtriggerCord work perfect with the K10D.
So lenses can be corrected for back- and frontfocus.
07-23-2021, 09:52 AM   #11
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I took similar test shots with an adapted M-42 50mm Super-Takumar lens. Just for completeness I used similar lens openings as I did with the kit zoom, about f/6.7. I couldn't see any blurry parts on any part of the frame in the test shots I took with the Takumar.


I think this confirms that the blurriness is caused by the kit zoom lens. Is there anything I could do myself to improve or fix it? Maybe there's some screw I could tighten or a glass element to re-position inside the lens? There's even disassembly instructions on Flickr for this lens.
Pentax 18-55 DA II Disassembly/Reassembly | Flickr


Or, if there's no remedy for this problem, maybe I should just stop worrying about it and just keep using the lens.
07-23-2021, 10:48 AM   #12
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From what I have heard, and no doubt someone will correct me should I be wrong, the 'Kit Lens' is just that - a reasonable lens sold with a body so that the lucky purchaser can get started immediately (after charging the battery and installing a suitable SD card). Many people are completely satisfied with the kit lens' performance, but other, possibly more discerning, users become aware of its shortcomings, and look at other options, of which there are many. You have indicated that using a pre-digital prime lens has given results with which you are happier - have you thought about augmenting your lens stable with more modern autofocus lenses ? (I know, the dreaded GAS !). You mention using the equipment on a tripod - I believe that, if you use the 2-second self timer, it can provide assistance if the problem is camera movement. You could also try another example of the kit lens, just to confirm it is the lens not the K10 itself.
07-23-2021, 03:12 PM - 1 Like   #13
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I would not even think about trying to repair or adjust a kitlens.

Not worth it.
Buy something better or check PK-Tether or PK Trigger Cord!


But really, get a better lens.
07-24-2021, 12:59 PM   #14
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Sad to hear that kit lenses can't be adjusted, although that is to be expected.

My dream (zoom) lens is the old version of Tamron SP 17-50 f/2.8. Currently that one seems to fetch prices around $260 new ($220 used). I will definitely consider getting that one in future if my budget allows. It has great reviews here: Tamron 17-50mm F2.8 SP AF XR LD Aspherical IF Di II Lens Reviews - Tamron Lenses - Pentax Lens Review Database

Would you recommend replacing the SMC DA18-55 with an old Pentax-F zoom lens? Those would work with the K10D in all shooting modes. I would lose the wide angle end with an F lens but that wouldn't be a problem for me. I tend to use the 30-40mm range the most with my current DA18-55, so I think I'd be using the wide end the most with those F lenses.

I did a quick check at a local used camera shop and found a non-SMC Pentax-F 28-80mm f/3.5-4.5 with a very slightly scratched front element for $35. There's also an SMC Pentax-F 35-80mm f/4-5.6 for $30.

Last edited by artrasa; 07-24-2021 at 01:25 PM.
07-24-2021, 01:54 PM - 1 Like   #15
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I would rather recommend you try to find a DA 16-45 in good shape.
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