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08-13-2007, 05:28 PM   #1
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Da*16-50 vs. Tamron 28-75

Well, my Da* 16-50 arrived today and I have run the gamut of emotion from elation to dissapointment. Yes, the lens focus quietly, and a little faster than the non Da*, and looks and feels nice, but at f2.8 it is not as sharp as the Tamron. The difference, which is really noticable at %100 might make me return the lens; though I want to shoot some more photos with it, as it is a more useful focal range for me than the Tamron on a DSLR.
All these were taken on a tripod, in JPG, at ISO 100 with the 2s timer shutter release.

Pentax 28mm f2.8


Tamron 28mm f2.8


Pentax 50 f2.8


Tamron 50 f2.8


I really like the way the Da* renders the the overall image better, but sharpness is important. I am just a little disappointed right now that this copy does not equal the performance of the Tamron. I am curious if others who own both lens have done any comparisons.

08-13-2007, 06:00 PM   #2
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I wouldn't be happy at all with those results...hope my DA* 50-135 is as good as expected.
08-13-2007, 06:01 PM   #3
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i think you have a really bad copy of that lens
08-13-2007, 06:10 PM   #4
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QuoteOriginally posted by MJB DIGITAL Quote
i think you have a really bad copy of that lens
I hope you are right and they are not all this soft. I am really not a "pixel peeper", but I do not find the IQ at f2.8 acceptable. I think I will exchange it at B&H and hope for a better copy. Of course if it is a bad copy, it doesn't give me a lot of confidence in quality control, either.

At f8 things do improve(but I didn't buy it to shoot f8 constantly):
Pentax 50mm f8: same testing procedures as above.


Tamron 50mm f8


08-13-2007, 06:10 PM   #5
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Wow... That Tamron is a freakin sharp-ass lens at 2.8! And for only about $375? Can it be true?
08-13-2007, 06:13 PM   #6
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QuoteOriginally posted by Dr_Watso Quote
Wow... That Tamron is a freakin sharp-ass lens at 2.8! And for only about $375? Can it be true?
Yeah, it's all true...she is amazing.
08-13-2007, 06:28 PM   #7
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Have you tried to manually focus to see if image gets sharper. The problem may not be the lens but the focusing system.

I have been seriously considering this Tamron. I have the 90mm macro and it is very sharp.

Just curious.

Denis
08-13-2007, 06:31 PM   #8
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QuoteOriginally posted by Denis Quote
Have you tried to manually focus to see if image gets sharper. The problem may not be the lens but the focusing system.

I have been seriously considering this Tamron. I have the 90mm macro and it is very sharp.

Just curious.

Denis
That is a good suggestion. I am going to try that tomorrow. I didn't realize the issue until I was viewing the images on the computer. I did ponder that though as I searched the photo for a sharp area, thinking there was some front or back focussing going on. My problem was I didn't find any area sharply in focus. Nonetheless I will try some manual focus tweaking tomorrow. Thanks.

08-13-2007, 06:48 PM   #9
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QuoteOriginally posted by Wethphotography Quote
That is a good suggestion. I am going to try that tomorrow. I didn't realize the issue until I was viewing the images on the computer. I did ponder that though as I searched the photo for a sharp area, thinking there was some front or back focussing going on. My problem was I didn't find any area sharply in focus. Nonetheless I will try some manual focus tweaking tomorrow. Thanks.
I hope the results change, but a quick google search shows you're not alone in your sharpness complaint. There is another person online who also has side-by-side with a competing lens, and a similar conclusion.
08-13-2007, 07:02 PM   #10
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The 16-50 looks way back focused. The fence is pretty sharp!
08-13-2007, 07:04 PM   #11
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How can you make a fair comparison between two different lenses of different focal lengths and of different lens construction? A fairer comparison is to compare with another lens of similar make and model. That would remove any doubts that the problem is with the lens?
08-13-2007, 07:32 PM   #12
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I think the point is that while there is a possibility of a bad sample, there is also the possibility that the Tamron may be superior in terms of IQ...
08-13-2007, 07:34 PM   #13
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QuoteOriginally posted by creampuff Quote
How can you make a fair comparison between two different lenses of different focal lengths and of different lens construction? A fairer comparison is to compare with another lens of similar make and model. That would remove any doubts that the problem is with the lens?
You make an interesting point. But, I fear you misunderstood the purpose of my post. If so I apologize for not being clear. first I was not attempting a full comparison between the two, merely comparing two focal lengths that both lenses have in common to illustrate my concern that the Pentax is not as sharp at 2.8 as the Tamron. A fact that anyone considering this lens might want to know. I understand the focal lengths differ. In terms of lens construction though, that should favor the Pentax, unless you are refering to the Tamron being a full frame lens and the Pentax digital only. I am merely sharing my results with one copy of a lens as compared to a copy of another lens in a focal range they share. Given the wide-open performance of this copy of the Pentax lens, I am not willing to trade the Tamron's sharpness for the wider focal length of the Pentax. You might reach a different conclusion. I personally had hoped to replace the Tamron with the Da* 16-50 and 50-135. But I won't do that if the image sharpness wide-open isn't as good. Again, you and others might make another choice. "An informed consumer knows the consequences of their purchase."
08-13-2007, 07:49 PM   #14
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Looks like back focus or really bad back focus if you can't even see the area of focus. Either that or actually I'm noticing that in the DA* images, there seems to be a bias in focus towards the right side of the photo. Maybe you should try the centered AF mode. If not and maybe the folks here are right about a bad copy.

I looked up on the Tokina DX 16-50 on photozone and that copy was shown to have decentering and the wide aperture IQ was rather crippled and then got much better stopping down. There's probably some decentering going on here with your DA* so yea, I'd get it fixed.

Last edited by FotoPete; 08-13-2007 at 07:56 PM.
08-13-2007, 08:12 PM   #15
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QuoteOriginally posted by FotoPete Quote
Looks like back focus or really bad back focus if you can't even see the area of focus. Either that or actually I'm noticing that in the DA* images, there seems to be a bias in focus towards the right side of the photo. Maybe you should try the centered AF mode. If not and maybe the folks here are right about a bad copy.

I looked up on the Tokina DX 16-50 on photozone and that copy was shown to have decentering and the wide aperture IQ was rather crippled and then got much better stopping down. There's probably some decentering going on here with your DA* so yea, I'd get it fixed.
Pete, thanks for the research. I will reread that review. I was in centered AF mode and I checked before each photo that the sensor was illuminating on a small juniper planted in the middle between the front and rear wall. Forgive my technical ignorance, but what is decentering and can it be fixed? I guess I will call Pentax tomorrow and see what I can learn. My dilemna is: do I send it to Pentax to try a repair or return to B&H while I can and buy another. Anyway thanks for the insight. I will now go off and grumble while I point my browser to Photozone...
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