i have the canon 40D and as you all know my 17-85mm is not wide enough sometimes.i want to buy a zoom lens starting from 10mm ,but it turns out that is not a very easy choice.there's canon 10-22mm, sigma 10-20mm ,tamron 10-17mm, and the new tokina 11-16 mm.i know that 11-16mm seems more like a prime lens but is f2.8!!! if if have any of these lenses, please tell me what you think i should do.sigma is cheaper, but has only one year warranty ,tokina seems better optically and has 3 years warranty but is more expensive.


thank you