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05-28-2012, 05:44 AM   #1
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Tamron 10-24mm auto focus problems.

Having had problems getting this lens to auto-focus correctly (it seemed unable to focus on far subjects, and I've had to resort to manual focus (of all things! )) on my K-5, I tried this weekend to set up the focus fine adjust. In doing this I found that:
  • If I try to auto focus using live view it gets it pretty much spot on.
  • If I switch to non-live-view then the focus is set, incorrectly, further away. In this case by about 6" at 3' as indicated on the focus ring.
This would explain the problems I've been having with shooting landscapes - it would have been trying to set the focus past infinity. The testing was done using spot focussing, tripod mounted, shooting my latop screen displaying a Moire pattern target on it, as seen here AF microadjustment for the 1Ds mark III, 1D Mk3, 5D Mk2, 7D.

Has anyone else been having problems like this? Is it a 'feature' or a 'bug'? If a bug is there anything I can do about it (apart from buying a new lens and/or camera that is)?

05-28-2012, 08:36 AM   #2
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Mine will do that on occasion where it will not focus at 10mm, but if I bump it to 10.6-11mm it generally will autofocus.
05-28-2012, 08:41 AM   #3
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Although this is (perhaps) a different issue, I posted a question about autofocus on my K100 and K200 with the (older, slower) 10-20mm sigma. Basically both bodies typically, but not always, autofocus distant objects at just over 3ft (10mm focal length.) At longer focal lengths (like 20mm), the cameras autofocus more accurately (per the lens scale markings.) I've since tried the lens on a K-5 with identical results, and then repeated the tests with an entirely different copy of the 10-20mm, with the same results.

From the responses, everyone elses' cameras autofocus the lens at correct scale readings.

Paul
05-28-2012, 09:51 AM   #4
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my copy tend to have agony to focus when is on F8 and above on 10mm, opening to 6.3 or 7.1 solves problem usually.

05-28-2012, 10:48 AM   #5
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Posting pictures and explanations on where and how you tried to focus would help. Often, people have trouble with AF on ultra-wide lenses because the lenses render subjects so small in the viewfinder that they don't cover the full range of the AF sensor, so the camera ends up focusing on something in the background instea.d You have to choose your focus targets carefully to avoid this behavior, which is inevitable to some extent but especially problematic with ultra-wides.
05-28-2012, 11:03 AM   #6
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I haven't had problems with my 10-24 on my K20D but I have an idea of what to avoid. I don't try to AF on infinity at 10mm! Especially not with Auto / Multipoint AF and a wide aperture. The subject field is just too target-rich, and the DOF isn't thick enough to cover for some misfocusing. Problematic center AF may be similar if there are multiple targets in the center AF zone. And as with macro, AF really isn't our friend when shooting 'scapes. Much better to visually MF on the exact point I'm most interested in, with the aperture stopped-down enough to cover the DOF range desired.
05-28-2012, 01:05 PM   #7
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Thanks for the answers guys. I understand the points about shooting landscapes in the field, and they make sense. However in my controlled experiments I was, as I say above, shooting my laptop screen from about 3', with the target therefore covering about 1/3 of the field of view. It was tripod mounted with spot focussing aimed at the centre of the screen. In each case I wound the focus out to infinity and the half pressed the shutter button. With LV on the focus got set correctly, with LV off, the focus was off by about 6" as indicated on the focus ring.

I'll have another go a bit later. Can I post videos here?
05-28-2012, 01:14 PM   #8
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I would think a link from youtube should work for that.

06-28-2012, 04:17 PM   #9
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QuoteOriginally posted by Barbarosa Quote
my copy tend to have agony to focus when is on F8 and above on 10mm, opening to 6.3 or 7.1 solves problem usually.
Mine is behaving exactly like you say.
I think it could be a bug in the K-5 firmware (?hardware), because it just doesn't happen on my K-7

Cheers
06-30-2012, 04:55 PM   #10
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My Tamron can also have some difficulty auto focusing at 10-13mm on my K20D, so I switch to MF. It focuses fine on my daughter's k-x at all lengths. I never use liveview so I don't know if that would make a difference.
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