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11-14-2012, 06:54 AM   #16
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i think the best will be to try another body.

11-15-2012, 03:23 PM   #17
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My 17-50mm is impossible to get accurate focus throughout the range without using in-cam adjustment. This is after servicing it at Tamron japan to get it even in the ballpark..

Mine will be tack sharp from F2.8 -> F5.0 on one reasonable adjustment (+2 or 3) and as soon as I go to F5.6 or greater its miles off. I can in-cam adjust it to be tack sharp for the smaller apertures, but then if I want it wide open I need to do in cam adjustment again.

I've just consigned myself to using it from F2.8 -> F5 which is pretty poor but better than nothing and one less thing to worry about fussing about in cam .. but thats what I get for purchasing a notoriously unreliably focusing lens second hand.

All my other zooms are reasonable, although they do vary a wee bit with FF/BF nothing drastic enough to be annoying.
11-15-2012, 03:54 PM   #18
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The focal point of a lens wide open isn't necessarily the same as when closed down. I think you've got glass with bad focus shift What is Focus Shift?
11-15-2012, 04:11 PM   #19
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QuoteOriginally posted by SteveB Quote
The focal point of a lens wide open isn't necessarily the same as when closed down. I think you've got glass with bad focus shift What is Focus Shift?
Kind of odd for a modern AF lens, though isn't it? I recently discovered this for the first time with a 30 year old lens, but I would think this would be considered unacceptable in any modern design...

11-15-2012, 04:37 PM   #20
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unfortunately i was planning for one lens only and its the Tamron 17-50. In fact its the only lens im using since my EOS 300D. i'll have to switch back to Nikon/Canon if it doesnt work on a pentax.

by the way: Pentax UK is taking a look at my pics....
11-15-2012, 04:39 PM   #21
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QuoteOriginally posted by SteveB Quote
The focal point of a lens wide open isn't necessarily the same as when closed down. I think you've got glass with bad focus shift What is Focus Shift?
Very interesting, CDAF works perfectly on mine too which I had expected. I do wish you could get per aperture AF adjustment or at different zooms (i've had different results with zoom lenses same aperture at different zoom levels).

That said the Tamron has aspherical elements in its construction afaik so it shouldn't be a worry.

Last edited by FruitLooPs; 11-15-2012 at 04:46 PM.
11-15-2012, 08:12 PM   #22
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QuoteOriginally posted by mckracken Quote
Pentax UK is taking a look at my pics....
Too bad we can't see them.
11-16-2012, 01:09 AM   #23
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QuoteOriginally posted by SteveB Quote
The focal point of a lens wide open isn't necessarily the same as when closed down. I think you've got glass with bad focus shift What is Focus Shift?
QuoteOriginally posted by FruitLooPs Quote
Very interesting, CDAF works perfectly on mine too which I had expected. I do wish you could get per aperture AF adjustment or at different zooms (i've had different results with zoom lenses same aperture at different zoom levels).

That said the Tamron has aspherical elements in its construction afaik so it shouldn't be a worry.
It might have more to do with the sensitivity of the PDAF points. The K30 has only f5.6 sensitive AF points that make them less precise for wider apertures. The K5II should have less problem in this respect.

11-16-2012, 02:02 AM   #24
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QuoteOriginally posted by soalle Quote
It might have more to do with the sensitivity of the PDAF points. The K30 has only f5.6 sensitive AF points that make them less precise for wider apertures. The K5II should have less problem in this respect.
I often use the fa77 wide open with the k30 and it very rarely misses focus.
11-16-2012, 06:51 AM   #25
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QuoteOriginally posted by vonBaloney Quote
Kind of odd for a modern AF lens, though isn't it? I recently discovered this for the first time with a 30 year old lens, but I would think this would be considered unacceptable in any modern design...

For the new lens I don't think it is a matter of poor design but rather of a faulty lens. Either a manufacturing defect or subsequent damage due to a drop or something. (As for older lenses spherical aberration used to be quite common on all but the most expensive lenses)

Having a lens element positioned just a fraction of a mm from where the design requires it to be can easily introduce a large amount of spherical aberration (among other things). In a zoom lens there is even more to go wrong since there is a lot of precision co-ordinated movement of various elements that can easily go wrong if something gets broken or goes out of calibration.

In practical terms the first thing to do is try the lens on another camera and try another lens on the camera. That should tell you which one is at fault. If it is the lens then the only thing to do is send it for repair.
11-16-2012, 09:10 AM   #26
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Just came back from testing another k30 body.
the same thing. AF unusable from 5.6. (tested with yet another lens)

Lens: Tamron 17-55 2.8
Im postive this is an official problem of the k30 with this Tamron lens.

I hope Pentax UK will take notice and release a firmware update. (hope this can get fixed with a firmware update...)
11-16-2012, 10:37 AM   #27
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QuoteOriginally posted by mckracken Quote
Just came back from testing another k30 body.
the same thing. AF unusable from 5.6. (tested with yet another lens)

Lens: Tamron 17-55 2.8
Im postive this is an official problem of the k30 with this Tamron lens.

I hope Pentax UK will take notice and release a firmware update. (hope this can get fixed with a firmware update...)
Why would Pentax try to get their camera to work properly with a non-Pentax lens? Have you noticed how the lens correction options in the K-30 menus for distortion and CA are greyed out for 3rd party lenses? That's significant I would say, if not precisely related to your problem. I think there would have to a lot of direct complaints to Pentax to stand any chance of action on their part.

I've read many reports of severe focus problems with the Tamron 17-50 on Pentax bodies well before the K-30 was released; a shame as it would be the best lens of its type otherwise. I'm quite relieved that my Sigma 17-70 works perfectly on my K-30, there was no guarantee it would.

Last edited by SteveB; 11-16-2012 at 10:44 AM.
11-16-2012, 10:46 AM   #28
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QuoteOriginally posted by SteveB Quote
I've read many reports of focus problems with the Tamron 17-50 on Pentax bodies well before the K-30 was released;
Yep, and the 24-75 as well. Tamron and Pentax don't always play well together.
11-16-2012, 10:48 AM   #29
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Why would Pentax try to get their camera to work properly with a non-Pentax lens?

What kind of attitude is that? Or to answer: Because they want to sell cameras? This is not some obscure lens we are talking about. The Tamron 17-50 2,8 is probably the most popular wideangle zoom aps-c available. And i bet you a dime and a dollar it sells better than the overpriced (and inferior from what ive heard) pentax 16-45. (not to mention that its a 4.0 lens)

Last edited by mckracken; 11-16-2012 at 10:56 AM.
11-16-2012, 11:01 AM   #30
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QuoteOriginally posted by mckracken Quote
Why would Pentax try to get their camera to work properly with a non-Pentax lens?

What kind of attitude is that? Or to answer: Because they want to sell cameras? This is not some obscure lens we are talking about.
If a 3rd party lens does not work properly with the body, but Pentax brand lenses do, why is that Pentax's fault? They need to sell glass too, bodies are not their big money maker, glass is. They probably aren't purposely sabotaging the Tamron glass, but why should they modify their body to work with glass they did not make?

Tamron does not license the use the K mount from Pentax, I don't believe they have licenses from any of the manufacturers, they reverse engineered the system to make them work. Just like Metz and Sigma reverse engineered the flash system, almost every updated body require a firmware update to the Metz and Sigma flashes to make them work properly again, yet an old Pentax AF360 that was bought years ago for a *istDL will work fine on a K-30 with no update.
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