Thanks Snoweagle. I've done some test with/without a cheapo 20$ kenko UV filter on a efs 10-22mm (77mm) and efs 18-55mm (58mm) with different aperture,settings,etc but I can't seem to pinpoint the difference. Are there some tests that I can perform to justify buying the more expensive brands?
Btw, I compare the images on 100% cropped.