Hey everyone, So I've been hearing about this amazing lens, the 17-55 f2.8 IS. Reading review after review people constantly raved about it's amazing optical qualities. Now I happened to run onto these technical reviews by photozone.de: 17-55 18-55 In it they individually test the lens' MTF, CA, and distortion. I then compare them and I find the differences in all sections...tiny. Also, according to those tests, the 18-55 is superior optically than the 17-55! I know that there are extra things to the lens than IQ (USM, build, AF etc) but I'm on a budget and spending $1300 CAD on a lens for those stuff seems unnecessary at my level. I currently have the Sigma 30mm f1.4 and the 18-55 IS. I was originally hoping on selling both and replacing them with the 17-55, but now i'm not so sure. Are those lab tests, just tests? For those of you who have used both lenses, are the differences greater in the "real world"? Otherwise, I might just spend $400 on a flash. Thank you for any info!