Quote Originally Posted by clemmb


I tested the tamron 17-55 and my 25-105 both on my XTi(same body). Both lenses wide open(tamron at f2.8 & 35mm, canon at f4 & 35mm), same ISO, etc...


The 24-105 is noticably sharper.


I know my test is not scientific but I have always gotten sharper photos from my 24-105.


Interesting. Thank you for sharing your results. The only time I had the 24-105 was back when I had the 20D and 5D. On the 20D, I got sharper results from the Tamron 17-50 than the 24-105 (at 35mm anyway... 17mm on the Tamron has a lot of field curvature). It's possible that I've been wrong about the 17-50 being sharper than the 24-105 all this time. (The 20D doesn't have liveview, so it's difficult to be 100% certain of critical focus, even when taking a lot of shots with focus bracketing. That may have affected my results.)