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02-01-2010, 12:02 AM   #1
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Tamron 17-50mm vs 28-75mm

Thought I'd post some crops comparing between the Tamron 17-50 and 28-75 lenses. I used the 28-75 first and was thrilled with the results from day 1. Received a copy of the 17-50 on Thursday and wanted to compare it with its big brother.

Test conditions:
Tamron 17-50 mounted on Pentax Kx
Tamron 28-75 mounted on Canon Xti (400D) - a 10 MP camera

Both cameras tripod mounted. Pentax output DNG. Canon output RAW (CR2).
All images loaded into Photoshop CS3 and processed with default parameters with exception of WB and exposure. To equalize the brightness in images, I adjusted the exposure. The Canon Xti AWB sucks so I had to adjust WB manually in Photoshop.

Focus on the Pentax was done through Liveview and MF via magnification. Sorry, the Canon Xti has no LiveView, and the viewfinder is just too small and dark for accurate MF so I just used AF. Focus point was the right red cheek on the sunshine toy.

So yes, we are dealing with two different cameras, but when you see the results, IMHO the resolution differences between the two cameras was not a major factor in the results. Feel free to disagree.

Please ignore the colour differences...the WB was probably the reason for the difference.

First, here is the overall scene from where the crops were made:



02-01-2010, 12:04 AM   #2
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50mm crops:
In all crops the first row, from left to right is Tamron 28-75 @f2.8, f4, f5.6, and f8
Second row, from left to right is Tamron 17-50 @f2.8, f4, f5.6, and f8

Centre crop



Bottom crop


Right side crop
02-01-2010, 12:06 AM   #3
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35mm crops:
In all crops the first row, from left to right is Tamron 28-75 @f2.8, f4, f5.6
Second row, from left to right is Tamron 17-50 @f2.8, f4, f5.6

Centre crop
(the rightmost picture on the first row is Tamron 28-75 @f8)



Bottom crop


Right Crop
02-01-2010, 12:27 AM   #4
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The first 2 posts look great, but your last pics, in post 3, are not showing for me.

02-01-2010, 01:06 AM   #5
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The Pentax Kx Tamron 17-50 looks better to me.
02-01-2010, 01:27 AM   #6
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The color is a better on the Kx w 17-50, so it is a bit misleading. But. for sharpness, the 2 lenses perform very similarly--they do look like brothers.

I would hesitate to call it one way or the other, unless the colors could be balanced better, then it might be possible. I would say the lenses, for all practical purposes are nearly identical, with a couple of small differences in sharpness wide open (17-50 slight edge) and in the bottom crops (28-75 slight edge). The choice in lens, from this test here, is a matter of what focal length is better for your needs--IMHO. Surely, sample variation would wash out any differences seen here.
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