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12-16-2008, 10:12 PM   #16
Gus
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I have front focusing with the same lens on a K20D. Seems to do alright with the per-lens adjustment set between -8 to -9 in the range of 17-35 but it seems to be beyond redemption at 50 (can still see visible FF even after setting the camera to -10). I didn't get the time do any serious testing, but I did play with a focus chart for about half an hour.

This is my first non-Pentax lens and I'm a bit disappointed. I really wanted a fast wide angle zoom for indoor use and I didn't want to go through the hassle of testing various samples of the 16-50 Pentax. I can quickly learn to compensate for the underexposure problem (when stopping down) but the inconsistent focus is really off-putting, especially that it doesn't have quick-shift and that its manual focus has such a short run.

12-17-2008, 07:41 AM   #17
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QuoteOriginally posted by Marc Sabatella Quote
Could well be that the Tamron has an FF problem - unless you were testing in tungsten light, in which case the ztamron might be fine, and the Sigma might have a *backfocus* problem that the tungsten light is masking.

That's for the focus test charts. When I say the results were meaningless for the remote control, I mean they were meaningless- no point trying to assign any meaning to them. The camera will focus on whatever it pleases. Could be totally coincidence that it chose the "right" button when the Sigma was mounted - ther'e absolutely no way to know, so there is no point even thinking about it.
Mainly tested indoors with main light source 30W CFL Daylight ~150w bulb on and off same front focus issues for Tamron. But spot on AF for pentax FA50 1.4, sigma 18-50mm ex dc macro 2.8, sigma 105mm 2.8 macro and tamron 70-300mm 1:2 macro lenses.

QuoteOriginally posted by Gus Quote
I have front focusing with the same lens on a K20D. Seems to do alright with the per-lens adjustment set between -8 to -9 in the range of 17-35 but it seems to be beyond redemption at 50 (can still see visible FF even after setting the camera to -10). I didn't get the time do any serious testing, but I did play with a focus chart for about half an hour.

This is my first non-Pentax lens and I'm a bit disappointed. I really wanted a fast wide angle zoom for indoor use and I didn't want to go through the hassle of testing various samples of the 16-50 Pentax. I can quickly learn to compensate for the underexposure problem (when stopping down) but the inconsistent focus is really off-putting, especially that it doesn't have quick-shift and that its manual focus has such a short run.
sorry to hear Gus, don't give up. I'm dead set on getting a good copy to compare with my sigma 18-50mm ex dc macro 2.8

Unfortunately, due to Xmas replacement might not be available until after Xmas for me
12-17-2008, 10:59 PM   #18
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Update:

Looks like, I'm getting an advance replacement Tamron 17-50mm 2.8 (pentax) for my front focusing proned one so hopefully arrives tomorrow or Monday and is a good copy - I'd be able to compare a good copy Tamron 17-50 2.8 vs a front focusing proned Tamron 17-50mm 2.8. Fingers and toes crossed
12-17-2008, 11:14 PM   #19
Gus
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QuoteOriginally posted by eva2000 Quote
sorry to hear Gus, don't give up. I'm dead set on getting a good copy to compare with my sigma 18-50mm ex dc macro 2.8

Unfortunately, due to Xmas replacement might not be available until after Xmas for me
Well good luck with your quest

And an early merry Xmas!

12-18-2008, 01:55 AM   #20
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QuoteOriginally posted by eva2000 Quote
sorry to hear Gus, don't give up.
Second that. Don't give up. You should be able to get a good copy. I've only heard good things about the lens. Would be a shame not to use it because of FF/BF issues.


QuoteOriginally posted by eva2000 Quote
I'm dead set on getting a good copy to compare with my sigma 18-50mm ex dc macro 2.8
Sounds interesting. Please keep us posted! It'll be nice if you could post a link here to a new comparison thread.
12-19-2008, 03:53 AM   #21
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QuoteOriginally posted by Gus Quote
Well good luck with your quest

And an early merry Xmas!
thanks and Merry Xmas to all as well

QuoteOriginally posted by Class A Quote
Second that. Don't give up. You should be able to get a good copy. I've only heard good things about the lens. Would be a shame not to use it because of FF/BF issues.



Sounds interesting. Please keep us posted! It'll be nice if you could post a link here to a new comparison thread.
will do, replacement lens was sent out today so i should receive it Monday for a quick compare with FF one then send the FF one back
12-22-2008, 05:45 AM   #22
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Replacement has arrived .. part 2 https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/44702-tamron-1...-part-2-a.html
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