Quote (Eek @ Aug 5 2010 12:14am)
I wouldn't bother with a UV filter unless you need it to complete the weather sealing.. but i doubt you'll go out in bad weather with a XTI. Most UV filters degrade image quality unless you're willing to spend the extra on a high end b+w multicoated UV filter. I don't use any protection filters with my lens now, my hood protects it well enough.
Also, like lithfkn said, 24 isn't really wide on a 1.6x crop factor. But you can probably solve that dilemma with the Sigma 10-20 that you already have. I'm absolutely in love with my Canon EF-S 15-85 IS USM. Sure it isn't as fast, but it's build like a tank, just as good as the other L lenses that i've own. AF is extremely quick and the 4 stop IS is a godsend in some situations. It's odd to say.. but the sharpness of the 15-85 is just as good as my 100L Macro.
If you're wanting something faster, there is always the 17-55 f/2.8. It's a L lens in a EF-S body :P. Build isn't as good but optically beats alot of "L"s including the 24-70.
I've compared my 50mm 1.8/f with the filter on and off in many different circumstances and I have yet to see even the slightest difference in image quality.
