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01-14-2010, 02:44 AM   #16
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Thanks for the correction, focal length was 16mm, F5.6 (sorry got messed up there). Photo was taken sitting on masonry to avoid tripod shake. Perhaps remote is worth a try (I have one)

Just tried the 18-55mm kit lens and it does a similar thing from 18-22mm: it cannot find focus when looking at infinity. And yes, regards your good suggestion, infinity was set to all the way (just past the infinity symbol). Thanks for the tip anyway.

01-14-2010, 02:53 AM   #17
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And I can hear definite click

At the 24mm mark I can hear a definite click: but I had to put my ear next to the lens. Does anyone else hear this please? Thanks
01-14-2010, 04:30 AM   #18
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QuoteOriginally posted by Stefan Carey Quote
Thanks for the correction, focal length was 16mm, F5.6 (sorry got messed up there). Photo was taken sitting on masonry to avoid tripod shake. Perhaps remote is worth a try (I have one)
I had a second look at that 16 mm photo, and even in this scaled down version, the right-hand side looks OOF, while the left hand side doesn't. I think your lens may be severely decentered. I've occasionally seen mild cases signs of a little de-centering on some portrait-oriented shots with my 16-45, which probably is due to the wobbly barrel, but nothing even remotely similar to this.

(If you could post a 100% crop from the mid-left and mid-right sections of the picture, it would probably be easier to see)
01-14-2010, 04:37 AM   #19
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These images certainly shed more light on the problem.
As Espen says your f/16 sample at infinity focus clearly shows a way off focus R hand side of the image but sharp L hand side, indicating decentering.
Is the 16-45 the only lens that exhibits this problem (not referring to infinity focus locking issues)?

01-14-2010, 01:00 PM   #20
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QuoteOriginally posted by gazonk Quote
Well, that's definitely front focused. Did you set it to the infinity marker? My 16-45 focuses a bit past the infinity marker, did you try that?

About the shutter release: Try the Pentax IR Remote, I'm pretty sure your K-m works with that. When I use my K10D on a tripod, I almost always use the IR remote with 3s delay.

EDIT: Btw. I was referring to the crop below the f/16 shot. I was wondering if that really could be f/16, but it's not, it's f/5.6 according to the EXIF.
I have found the K-m autofocus really ugly and unreliable. It focuses wherever it wants and normally i don't want the focus in the center so spot focus is out of question. My k-m is basically a digital manual focus camera. As it seems you returned it already i can't advise you to try it in other pentax model.
01-14-2010, 02:39 PM   #21
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Summonbaka and Ash thank yuo both. I am going to do a double check today at infinity and different focal lengths all at 5.6, at the same spot on the river, taking extra care to check the lens is all the way to infinity.

Yes, it seems odd I am getting so much variation between shots and within shots (ie left and right focus) I will also take the same photo with the kit lens which I know is working fine. (another assumption I will check today: perhaps it is the camera).

I will post more photos tonight.
01-15-2010, 12:02 PM   #22
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In general 16-45 is one of the sharpest zoom lenses by Pentax, my copy was quite sharp at F4 at 16 mm.
What you describing might be also problem with AF of your camera, I've seen it with my K10D body. It is started with the lens not able to focus at infinity and than got worth. Camera was back focusing and hunting a lot.


QuoteOriginally posted by Stefan Carey Quote
1. While testing out the brand new lens I find that it has a lot of trouble, and is often completely unsuccessful focusing on anything near infinity, from say 100 metres and further away. I am using center auto focus point with a K-m. I know how to help the camera focus by trying to find an edge to focus on.

Is this endless hunting normal? Is this a faulty lens? Do you have have trouble with the Pentax 16-45mm getting focus at longer distances?

I do not mind using manual focus, and for using hyperfocal distance, manual focus might be better than using the focus lock anyway (?). (Last night I used the focus chart and the camera and lens seem to be fine there.) But there are times when I need to take a quick shot where this gets in the way.

2. I have notice a dramatic difference in sharpness of fine detail at long distance (2-3km) between some shots taken on the same tripod (RAW). The distant detail, like a large steel electriciy tower, is blurry and on some shots not, and I am beginning to think that even with a two second mirror lock up, the tripod is still vibrating after I have pressed the shutter. My theory is that where I have been extra careful to press the shutter gently and not move the tripod, the shots are sharper. (Especially where the tripod head is extended.) Has anyone moved from a lightweight tripod to a heavier tripod because of this? I willpost some samples tonight.
01-16-2010, 03:31 AM   #23
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It gets weirder

After trying lots of shots yesterday, and then more today I have two photos taken by the same lens at different focal lengths, but each photo is sharper on the opposite side.

NB trees are blurred because of the wind.

One thing I have also noticed is that I can hear a click when I turn the barrel just past 24mm, then I realised anything below this "click", the lens will not autofocus, or give me focus confirmation focussing manually


These are JPGS from the camera using the natural setting, resized.






And here's one from a Pentax F 35-70mm, which seems better all round




Last edited by Stefan Carey; 01-16-2010 at 03:44 AM. Reason: more photos
01-16-2010, 09:45 AM   #24
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QuoteOriginally posted by Stefan Carey Quote
After trying lots of shots yesterday, and then more today I have two photos taken by the same lens at different focal lengths, but each photo is sharper on the opposite side.

NB trees are blurred because of the wind.

One thing I have also noticed is that I can hear a click when I turn the barrel just past 24mm, then I realised anything below this "click", the lens will not autofocus, or give me focus confirmation focussing manually


These are JPGS from the camera using the natural setting, resized.
Looking at the static parts of your first photo on the left (the markings on the street, the parked cars) and comparing them to the static parts on the right, it definitely seems like your tilt-shift lens needs servicing.
01-16-2010, 01:39 PM   #25
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You're right! And thanks AWO45 for your reply. Lens will be sent back. Auutofocus is fine with two other lenses. I checked backfocus/front focus with a macro lens yesterday and it is fine.

Thanks everyone for their help
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