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01-04-2011, 04:27 AM   #1
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DA*16-50 severe back focusing on k-x normal?

This is getting a bit .... annoying. My first copy of a 16-50 showed severe back focusing, the focal point was well forward of the front of the dof.

So $90 later back it went to adorama for a swap. Well the second copy arrived and it performs identically . This prompted me to test all my other lenses and I found overall there was slight back focusing, although the focal point was always within the dof. So I went into the debug menu and tweaked the focus so now all my other lenses are bang on or slight front focusing.

Unfortunately this was not enough to fix the severe back focusing of the 16-50. I can only get in focus images at the 50mm end and focusing under about 10 feet away or less. Wider or further away and it's back focusing by feet.

So what do I do? I'm nervous about shelling out another $90 to try another 16-50 if the first 2 copies are the norm rather than exception. I have a sigma 17-70 that is so-so in iq, but at least I can trust the focus. I've read the tamron 17-50 has bb/ff issues, hmmm, so that could get expensive too. Maybe I could get the 12-24 but it would be nice to have a good quality wide to normal 2.8 lens.

Anyone else has this trouble with the 16-50

01-04-2011, 05:49 AM   #2
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I dont want to be smart ass but check this
today before two hours I sow bunch of sheep on snow plane so stop and try to get couple images, used fa50 on f4 and when opened images on my laptop find that most of them are out of focus, mostly like front focus, because head of sheep was out and back was in focus.
First thought was frontfocus because freezing cold outside, but than i checked my camera and noticed that focus point was on auto not central and camera decided to focus on but instead of head, so check that first, and sorry if I just waist your time.
01-04-2011, 05:55 AM   #3
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Tamron 17-50 is reasonably cheap compared to other comparable lenses. Sigma 18-50 could be a choise but seems more expensive.

Try to do a focusing test
01-04-2011, 06:09 AM   #4
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No, absolutely not normal--do not tolerate it. Return it, immediately, for another one, or buy another lens.

My question is, where does this $90 come from? You should be able to return without any costs. What is this $90 all about?

01-04-2011, 06:36 AM   #5
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QuoteOriginally posted by Jewelltrail Quote
No, absolutely not normal--do not tolerate it. Return it, immediately, for another one, or buy another lens.

My question is, where does this $90 come from? You should be able to return without any costs. What is this $90 all about?

I'm pretty sure the $90 refers to the shipping costs (which are high because it is a US-Australia transaction). Not sure if that's one way or roundtrip
01-04-2011, 07:36 PM   #6
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QuoteOriginally posted by Jewelltrail Quote
No, absolutely not normal--do not tolerate it. Return it, immediately, for another one, or buy another lens.

My question is, where does this $90 come from? You should be able to return without any costs. What is this $90 all about?
The $90 is 50 for postage, 27 for insurance and a 10 dollar surcharge for some USA inspection thing.

I think I'll try another 16-50 copy but if that one doesn't work out I'll be 270 out of pocket and still no lens. Hopefully this doesn't happen. I was curious whether sdm lenses, or the 16-50 in particular have a tendency to BF. The screw drive lenses I've bought have always been ok.
01-04-2011, 10:54 PM   #7
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Another possibility may be sending both the lens and body for service to have them adjusted to work properly together...
01-04-2011, 11:36 PM   #8
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QuoteOriginally posted by sewebster Quote
Another possibility may be sending both the lens and body for service to have them adjusted to work properly together...
Trouble is I have 7 other lenses that focus just fine now, and the 16-50 is well within the 28 day return period.

01-05-2011, 11:14 AM   #9
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QuoteOriginally posted by twitch Quote
Trouble is I have 7 other lenses that focus just fine now, and the 16-50 is well within the 28 day return period.
Yeah... seems annoying. I've wondered about this myself... if I get a misfocussing lens, do I have to send ALL my lenses and the body back in so they can make sure everything works together? How much would that cost? My body doesn't even have the focus microadjust
01-05-2011, 11:25 AM   #10
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QuoteQuote:
twitch: I was curious whether sdm lenses, or the 16-50 in particular have a tendency to BF.
No, they do not have that tendency, but it can & does happen. So sorry for the mess this has brought you--please, keep us up to date on what you decide to do and how you make out.
BTW, with which body do you shoot?

JT
01-05-2011, 08:01 PM   #11
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QuoteOriginally posted by Jewelltrail Quote
No, they do not have that tendency, but it can & does happen. So sorry for the mess this has brought you--please, keep us up to date on what you decide to do and how you make out.
BTW, with which body do you shoot?

JT
I have a k-x, so only one adjustment across all my lenses is possible. Ive already done this and all have their focus point within the dof except this 2nd copy of the 16-50. Micro focus adjustment in the k7 or k5 is looking like a really attractive feature at the moment....
01-05-2011, 09:01 PM   #12
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QuoteQuote:
Twitch: I have a k-x, so only one adjustment across all my lenses is possible. Ive already done this and all have their focus point within the dof except this 2nd copy of the 16-50. Micro focus adjustment in the k7 or k5 is looking like a really attractive feature at the moment....
Thanks--Yeah, I should have read the thread's title--then I would have known the body. Anwyay, I don't know anything about the Kx, except what you tell me here and that it does high ISO well. Now that I'm aware of its limitations with focus adjustment, I'll probably steer clear of that body.

My K20 does micro focus adjusment too. What a lousy situation to be in.
01-06-2011, 02:21 AM   #13
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QuoteOriginally posted by twitch Quote
Micro focus adjustment in the k7 or k5 is looking like a really attractive feature at the moment
It doesn't/wouldn't help severe FF/BF issues. It really is just a microadjustment, i.e. you can fix small misfocus like a few centimetres. You can't correct severe focus issues, for example one lens I tried (and returned for refund) was front focusing by 10 centimeter, no microfocus adjustment can fix that. If a lens is really that bad, it needs repair / mechanical re-calibration.
01-06-2011, 03:44 AM   #14
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I bought a 16-50mm secondhand on here and also noticed quite severe backfocus at 50mm and f2.8. I have to adjust to +160um every time I mount the lens. I'm also using a K-x and I hope to try the lens on another body sometime.

Last edited by kari; 01-06-2011 at 03:50 AM.
01-06-2011, 03:49 AM   #15
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QuoteOriginally posted by kari Quote
I bought a 16-50mm secondhand on here and also noticed quite severe backfocus at 50mm and f2.8. I have to adjust to +160um every time I mount the lens. I'm also using a K-x and I hope to try the lens on another body sometime.
Interesting, thanks for posting. I guess that is an option to dive into debug mode every time I mount the lens..... Hmmmmm
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