Canon 17-40mm f/4 L USM Lens Review
Updated Mar 19, 2009
Canon's USM gives the lens lightning quick focus and allows for full time manual focusing. The 17-40mm f/4 L is parfocal - meaning that the lens focus does not change while zooming. I find that when focusing for wider shots zooming to 40mm to lock focus then zooming back out to compose and shoot results in more acurate focus then attempting to autofocus at 17mm.
Using the 17-40 on a 35mm film body for Digital SLR with a full frame sensor gives you a versatile wide angle lens. The view at 17mm is impressive and I often find it a challenge to make pleasing compositions with such a wide lens. Still, there are many times when having a lens that can "take it all in" is invaluable.
If you're looking for a high quality wide angle zoom for outdoor shooting, it's hard to beat the 17-40mm f/4 L. If you need f/2.8 in a wide zoom then you want the Canon 16-35mm f/2.8 L, which is about twice the price of the 17-40mm f/4 L.
Find more Canon 17-40mm f/4 L lens reviews at Canon-Reviews.com.