In search of a wide angle lens for my camera, I went to the local camera store and tried Canon's EF-S 10-22mm (16-35.2 35mm equiv.) F3.5-4.5. At 10mm, it's actually usable, with virtually no vignetting; I'm sure that's the crop factor working for me. I believe Tamron's version is 10-24, same aperture range; I've only tried that on a 35mm body, with extreme vignetting at the wide end, but you can escape that around 15mm. It could perhaps be an alternative to Canon's, but Canon's also appears to have less barrel distortion at the wide end. All that being said, I still want a faster lens...F2.8. Canon's got their million dollar version of a 14mm prime F2.8, which would translate to 22.4mm on an APS-C body. I'm yet to see what that looks like through the viewfinder. Sigma also has a 12mm (19.2mm) F2.8 that I might rent for a test drive. I got plenty of time to do the field testing before I actually drop some cash for one!