I'm currently on the search for a second hand or new supertelephoto lens and was looking at either the 300 or 400mm f2.8 IS USM lenses. Has anyone used either of these??? Has anyone used them with a 1.4 or 2 x teleconverter and what were the results like? I'm trying to decide between the lenses, I think the 300mm might get more use as it's just lighter, but the 400mm would be great also and I think i'd like the extra reach. What I want is something really really sharp, mostly for wildlife photography and a bit of sports. I'd like to take the lens on a trip to Alaska and Yosemite next year and i'm heading to Vail skiing this year and would like to take it there as well.
I'm hoping someone can shed a bit of first hand knowledge on the lenses. I don't want to get the 300mm lens and then wish I had the 400mm.
I wish there was somewhere nearby the stocked them so I could have a play.
Also, I was looking at a 300mm 2nd hand and the person says it doesn't have a serial number??? Where does he find the serial number on the lens, i'd like to ring canon to make sure it's not stolen.