11-02-2010, 08:24 AM
My preference, I will go for Sigma 17-50mm OS F2.8 too because of its amazing IQ, and next option is Canon 15-85mm IS, and if less than $500 lens, I will go for Tamron 17-50mm VC or non-VC. Canon 18-135mm IS has poor IQ at wide angle but good at tele end. But the three lenses above have good IQ throughout the entire focal length.