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04-01-2011, 10:20 AM   #16
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QuoteOriginally posted by darrenleow Quote
The minimum focusing distance is measured from the sensor plane and not from the front of the lens
Oh, well I learned something today. Thanks!

04-01-2011, 10:36 AM   #17
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QuoteOriginally posted by BlueBubbleBoy Quote
I also noticed how much closer mine focuses that 11 inches. I hope I can get the sharpness thing figured out because I love the 2.8 and my copy focuses quickly and accurately.
When comparing the Tamron with my kit lens, I noticed the biggest difference in sharpness was at f5.6 at the long end. Is your lens sharper than the kit lens there? Like Jewelltrail said earlier in the thread, make sure to test it with real life shots and not just focus charts.
04-01-2011, 08:27 PM   #18
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QuoteQuote:
Blue Bubble Boy: I really can't find any difference in out of camera RAW sharpness from the kit and the 17-50. I'm a little frustrated but I'm hoping to do some more with the lens this weekend to see what the results are.
I owned both & have a couple of things to say. First, here are the Photozone MTF scores for the Tammy @ 17mm Wide Open, & the Kit @ 18mm, @ f8


Tamron 17-50 f 2.8 on 10MP Body and @ 2.8
17mm
Center: 2157
Border: 1856
Extreme:1751.5

Pentax 18-55 3.5-5.6 on 10 MP body and @ f8
18mm
Center: 2136
Border: 1880
Extreme:1484

The Tamron, wide open, easily outperforms the Kit f8.


Secondly, take one shot with each lens, at infinity--load them on your PC's monitor and have a look. Resolution differnce is astounding.
04-01-2011, 09:02 PM   #19
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QuoteOriginally posted by krp Quote
When comparing the Tamron with my kit lens, I noticed the biggest difference in sharpness was at f5.6 at the long end. Is your lens sharper than the kit lens there? Like Jewelltrail said earlier in the thread, make sure to test it with real life shots and not just focus charts.
QuoteOriginally posted by Jewelltrail Quote
I owned both & have a couple of things to say. First, here are the Photozone MTF scores for the Tammy @ 17mm Wide Open, & the Kit @ 18mm, @ f8


Tamron 17-50 f 2.8 on 10MP Body and @ 2.8
17mm
Center: 2157
Border: 1856
Extreme:1751.5

Pentax 18-55 3.5-5.6 on 10 MP body and @ f8
18mm
Center: 2136
Border: 1880
Extreme:1484

The Tamron, wide open, easily outperforms the Kit f8.


Secondly, take one shot with each lens, at infinity--load them on your PC's monitor and have a look. Resolution differnce is astounding.
I've been testing in the 35mm range between apeture of 5.6-7. I haven't been able to tell much difference between the two lenses if any at all. I do need try some at the wider ends and to be honest I've only looked at center resolution and not at the borders. I'll have to get out this weekend and take some test shots outdoors and then post them. I'm out of town and won't be back at my computer till after the weekend. Thanks for the suggestions guys. It is appreciated!

04-01-2011, 09:09 PM   #20
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QuoteOriginally posted by BlueBubbleBoy Quote
I've been testing in the 35mm range between apeture of 5.6-7. I haven't been able to tell much difference between the two lenses if any at all. I do need try some at the wider ends and to be honest I've only looked at center resolution and not at the borders. I'll have to get out this weekend and take some test shots outdoors and then post them. I'm out of town and won't be back at my computer till after the weekend. Thanks for the suggestions guys. It is appreciated!
Yes, 35mm on the kit, at these A's is the Sweet Spot of the Kit. But we need to look at the whole zoom range--these are not prime lenses. Also, even @ 35mm, f 5.6, take 2 shots with each lens & compare @ infinity--the difference (resolution) is astounding.
04-03-2011, 09:33 PM   #21
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Finally got back from our family weekend getaway and was able to put the test shots on the computer tonight. From what I can tell center sharpness at around 35mm and f/7.1 in the kit is pretty close to the Tamron. However in the borders the Tamron wins easily. On the long end of the lens the Tamron is also much sharper at all apetures. The only real problem I had was at the wide end with the Tammy opened all the way to f/2.8. It was way softer than the kit lens, however as I continued looking it seems as though the Tamron was just way off in the focus. It was BF quite a bit. I was focusing on a tree that was about 8 feet away, but it looks like it was focused several feet behind. Is this normal to hit it pretty well at other focal lengths except at the wide end? For example, I tried some "macro" type shots at 50mm and the focus seemed pretty accurate.
04-03-2011, 10:22 PM   #22
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QuoteOriginally posted by BlueBubbleBoy Quote
Finally got back from our family weekend getaway and was able to put the test shots on the computer tonight. From what I can tell center sharpness at around 35mm and f/7.1 in the kit is pretty close to the Tamron. However in the borders the Tamron wins easily. On the long end of the lens the Tamron is also much sharper at all apetures. The only real problem I had was at the wide end with the Tammy opened all the way to f/2.8. It was way softer than the kit lens, however as I continued looking it seems as though the Tamron was just way off in the focus. It was BF quite a bit. I was focusing on a tree that was about 8 feet away, but it looks like it was focused several feet behind. Is this normal to hit it pretty well at other focal lengths except at the wide end? For example, I tried some "macro" type shots at 50mm and the focus seemed pretty accurate.
Barry, @ 17mm the Tammy is sharpest--when focused correctly of course. To where is your AF point set? Did you aim at the tree & get focus confirmation, hold it to compose, then click? Any description of your technique could help us.

Last edited by Jewelltrail; 04-03-2011 at 11:13 PM.
04-04-2011, 08:18 AM   #23
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QuoteOriginally posted by Jewelltrail Quote
Barry, @ 17mm the Tammy is sharpest--when focused correctly of course. To where is your AF point set? Did you aim at the tree & get focus confirmation, hold it to compose, then click? Any description of your technique could help us.
I wish that was the case for me. I got this lens to use more at the wide end for landscapes and for some group indoor shots at wide apertures. I've provided a link to view an album with my test shots. You'll see, especially wide open, that the lens performs absolutely terribly. I'm not thinking its a focusing problem either.

My test setup: Camera mounted to a tripod and using a 2 second timer delay. Using center point focus, and yes, I'm waiting for the camera to lock on and beep before pressing the shutter all the way. I'd take a shot with one lens, leave the camera mounted on the tripod, remove the lens and replace with the next and take the photo with the same settings.

I did not include the photo of the tree I mentioned earlier, but I think the samples you'll see in the album are sufficient. Upon further inspection, I had focused on a very small branch of the tree and it looks like the wind may have blown a little causing me to miss focusing on the branch and hit behind it. The image was still extremely soft all around. All photos in this album are straight JPEGs from the camera and no processing done at all except for cropping and resizing.
https://picasaweb.google.com/bbjork06/TammyTest?authkey=Gv1sRgCL2qp8S_pJOIWQ&feat=directlink

I think I'm going to have to contact the seller and see if there is anyway I can return the lens. I'm going to get bit on the shipping, but I guess that was the risk I took. I'd appreciate any additional comments if you think I'm just missing something or doing something wrong. I appreciate the help!

Here's an acceptable image I got with the Tammy. No processing other than converting from RAW and resizing.
24mm, f/3.5, 1/600s



Last edited by BlueBubbleBoy; 04-04-2011 at 01:27 PM. Reason: Forgot to include link to album
04-04-2011, 01:25 PM   #24
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PS, I've contacted the ebay seller and he's going to refund the lens. I'll have to eat the shipping costs, but this lens is in desperate need of some adjustments and that would cost a lot more to me than shipping back an item to Japan.
04-04-2011, 06:53 PM   #25
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Looks like the lens has back focus or front focus problems. You could fiddle around with the focus adjustment: RiceHigh's Pentax Blog: K-x Debug Mode Tutorial - AF Adjustment
But then you risk messing up the autofocus on your other lenses. I suppose this is a risky lens to buy, but at least the seller is nice enough to refund it.
04-04-2011, 07:49 PM   #26
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I'm not convinced that it is a ff or bf issue. On some of the test shots I did wide open @ 17mm there was nothing sharp at all. And that's with infinity focus and a scene with plenty of depth. I am very grateful though that the seller is going to refund me. I'm still really interested in this lens though. A friend of mine shoots Canon and he's had several copies of the Tammy 17-50 in the Canon mount with no problems but I've seen plenty of people complaining of bad copies in the Pentax mount. I may just have to save up some more cash and buy new with awarranty. We'll see...

Last edited by BlueBubbleBoy; 04-04-2011 at 08:21 PM. Reason: typo
04-04-2011, 10:07 PM   #27
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QuoteOriginally posted by BlueBubbleBoy Quote
PS, I've contacted the ebay seller and he's going to refund the lens. I'll have to eat the shipping costs, but this lens is in desperate need of some adjustments and that would cost a lot more to me than shipping back an item to Japan.
Glad to hear it Barry--the only way to buy a lens new, if you ask me, is to go with a reputable dealer, who will stand by you until you are happy. I bought my Tamron 17-50 @ B & H--could I have found it cheaper--of course. When this lens is right, it is awesome, so I agree that sticking with it is a good idea.

Hoping to see some great shots from you with the 17-50 someday, soon.

JT
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