This goal had all the qualities on paper, I chose it for its 17mm F2.8 aperture and interesting zoom range. Installed on my Canon 450D results are not at the rendezvous: an average dive and a big problem "focus front." So I quickly redirected to a Canon lens and my choice fell on the 17-40 F: 4 L USM Canon EF - Zoom Wide Angle Lens 17/40 mm f / 4.0 L USM certainly more expensive but that is a marvel perfectly suited to the "small" 450D sensor (making it a superb 27-64). I rediscovered my case. Too bad but the Sigma / Canon torque does not seem to agree, at least in regard to this goal and 450D. Facing the Canon cited the old adage: "The market is always good too expensive" makes sens'surtout in the area of the photo. An excellent lens will still allow you to make the most of your case, the reverse is never verified with an average target.
