Quote Originally Posted by ckw
CAn you tell me is there a difference between the <span id="v4-1"]<span>Tamron AF 17-50mm F/2.8 Di-II LD Aspherical Lens and the one you've suggested?

ckw,


That's the lens. We just didn't go on and onand on and on with all the SP DII Asper etc.... stuff.


USM stands for "Unsharp Mask" and it is a sharpening technique that can easily be done from Photoshop CS# or even Elements.


In CS# it is under Filter/Sharpen you will see "Unsharp Mask" in the menu list. When you open it, there will be a preview box with a 100% zoom that has three settings "Amount, Radius, and Threshold" That is why I listed the figures as (200, .6, 0) Those would be the three values to enter. I find with my 40D that .3-.6 for the radius works really well. A threshold of 0 is fine because you are probably using ISO 100 and the image is clean. All that's left to do is dadjust the Amount. 150 - 300 are common values and you will see a big difference in the sharpness of you image.


That's why I'm saying you may want to hold off on replacing the Sigma 17-70 until you get a chance to work in a little sharpening. Is there anyway that you can post comparison images between you 60 macro and the Sigma 17-70 @60mm? Take two pictures of the same thing, both at f8. You may not need a new lens after all.


Last Note: As I said earlier, Lenses can vary in performance from copy to copy. I tested two copies of the Tamron 17-50 f2.8 DII when I purchased it and the first one was absolutely terrible. It wasn't a focus issue, it was an optic issue. The lens was terribly soft, even stopped down. The second was very sharp and I'm happy to say still being used today. So, It may be that you do have a bad copy of the 17-70 and need to send it back to Sigma to have it adjusted.


Hope these things help,


Chuck