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10-27-2011, 08:40 PM   #16
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What's wrong with the shots that the OP has posted? Are these supposed to be the problematic shots, someone enlighten me please.

10-28-2011, 02:18 PM   #17
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QuoteOriginally posted by ChopperCharles Quote
Problem is, even at f4 or f5.6 the Tamron is still missing focus, where my 100mm macro was dead on.
I was under the impression the macro was MF? Apples to oranges in that case. Otherwise, I'd say you simply don't have a well-controlled test with a large enough sample size to really make such a determination, and are instead seeing what you have already convinced yourself you will see.

If you *do* have such a well-controlled test, though, feel free to post pictures showing exactly where you focused and the method you used to focus, and then crops that demonstrate focus was anywhere but there. Then post the same for the macro. I'm still betting it will turn out the problem is something rather different than what you are describing. It's just a matter of common sense - if you have it adjusted so that it focuses correctly in tests but fails in "real life", there is no way the lens will suddenly start behaving just because the shooting conditions got more difficult. It's got to be a technique issue. Unless the tests were improperly performed, so your adjustments actually threw it out of whack.

QuoteQuote:
Also, the imgwide tag is NOT in the "go advanced" post menu.
It used to be - it was the second to last icon on the right. Now that one is apparently labeled "FANCYBOX", which is a new one on me.

Still, the point is, there was no reason to post such large images in the first place. A resized version to show context, then a 100% of the focus area would be more appropriate.

Last edited by Marc Sabatella; 10-28-2011 at 02:23 PM.
10-28-2011, 03:32 PM   #18
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Tamron's 28-75 has really bad QC...I went through 3 of them (BF/FF problems...one had a bad element that ghosted) before giving up.
They're great if you can find a good one. I wish they put as much work into the mechanicals as they did to the lenses :-P
11-01-2011, 05:39 PM   #19
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I don't shoot manual focus, especially not when the images count. Even with the split prism screen, the viewfinder is just too small and my eyes not up to the task. The images posted were from my Promaster AF 100mm f3.5 macro. KAF mount. (same as the Pentax, without the pentax coatings). I have no problems shooting with any of my other lenses, only the Tamron gives me problems reliably focusing, and not just at f2.8, but throughout the aperture range.

My dress rehearsal did allow flash photography, so that's what i used. it helped me keep the ISO low.

Large images were posted because I already had them on the web, and I just linked to them. Sorry 'bout that. I will use fancybox or whatever next time.


Charles.

11-01-2011, 06:03 PM   #20
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Okay, here's a sample of the constant issues I'm having with my Tamron. Center focus, aimed right at his face.



And here's a 100% crop



Sometimes it will front focus, sometimes it will back focus. i don't have problems with any other lenses' autofocus like i do with this tamron.

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11-01-2011, 09:12 PM   #21
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I used to have this lens but i sold this recently to fund other lens purchase. It is a good lens but it does have its quirks.

What aperture are u shooting that pic with?

Try to shoot with liveview on a tripod. Select the focus on the face. See if the pic is consistent with whatever u are experiencing now.

If it is, I am guessing the body backfocus/front focus and u may be able to adjust it using the AF adjustment on the body. While tuning the AF, set the Tamron to the longest end and test again.

Hope this helps.
11-01-2011, 09:33 PM   #22
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Brooke, that shot of the young ballet dancers shows off the capabilities of the K-5 (in the hands of a capable photographer like you). I raised all but the highlights with soft light, and it came out great, and that is just from a 124KB JPG.
11-01-2011, 09:34 PM   #23
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28-75 is known to have inconsistent QA, so you seems to have received bad copy. Having said that, I am a big fan of 28-75, many of my images I posted here are from 28-75.

11-01-2011, 11:11 PM   #24
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Looks to me like focus is on the door frame, behind the subject. Shots like this are difficult for testing purposes because it's not easy to control on what the camera will focus. This result could simply be a matter of the camera choosing to focus on the door frame instead of the subject's face. I've found the focus points are MUCH larger than indicators in the screen, so it's quite easy for this to happen, even if using center-point focus.

I think a more controlled test is in order. Though a bit over-the-top, something like this, perhaps: Jeffrey Friedl's Blog Jeffrey’s Autofocus Test Chart. This will allow you to have 100% confidence the camera focuses on the desired target.
11-02-2011, 07:27 AM   #25
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QuoteOriginally posted by thirdofthree Quote
I've found the focus points are MUCH larger than indicators in the screen, so it's quite easy for this to happen, even if using center-point focus.
I think that's what happened as well...the guy doesn't have much contrast on his face, so it locked on the door frame which looks very sharp. Try the test again w/ the guy wearing glasses (more contrast). I know...stupid, but would help us isolate the problem from body to lens...
11-03-2011, 01:00 PM   #26
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And the face probably doesn't completely fill the focus point. Indeed, this seems a classic example of the camera simply choosing to focus somewhere other than where you intended.nothing the lens can do about that.
11-03-2011, 01:24 PM   #27
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I am never unpleasantly surprised by the way my Tamron 28-75mm performs, while I, at least at first, was often pleasantly surprised by how good it was. That's not to say I don't get bad shots with the lens. It just means that it's my fault (or just impossible conditions) when I don't. Judging from my experience and what you posted, it sounds like you may have a bad copy (though a technique issue is possible). Is your Promaster lens the manual focus or auto-focus model? If it's auto-focus and works well, that lends credence to the probability that it is a bad copy of the Tamron. If it is manual focus, then perhaps you should test the Tamron with manual focus (although the focus ring doesn't have as much throw as a dedicated manual focus lens would), or just stick with manual focus lenses for the conditions you are shooting in.
11-09-2011, 09:38 AM   #28
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As i said, the Promaster is autofocus. I don't generally shoot manual lenses, I only have a few, and I'd never trust a manual lens to important action shots. If I have forever to set up a shot and can afford to bracket, sure.

I just picked up a Pentax-F 50mm f1.7 a few days ago, and so far I'm not having the same issues. Even at f1.7 I'm nailing focus more often than not, where the Tamron is still more often not focusing properly. I guess I'll look for another copy of the tamron, or maybe pick up the Tokina SV 28-70, f2.6-2.8 as they're reasonably priced. (I just wish there was a review or two of the SV model)

Charles.
11-09-2011, 06:43 PM   #29
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My tamron 17-50/2.8 has this inconsistant focus as well, when the subject doesn't almost fill the frame.

Last edited by pcarfan; 11-09-2011 at 06:49 PM.
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