Sigma 120-300 Questions

I have been on the cusp of buying the Canon 70-200 f/2.8 for some time now, but am now seriously considering the Sigma 120-300/2.8 OS in its place. My usual birding lens is my 400/5.6 and I don't really see being able to afford the 500/4 (which is the lens I really want) any time in the predictable future. The nice thing about the 120-300, is that I would have a 600mm with AF if I used it with a 2X (I lose AF with my 400 if I put on a TC, as I use it with my 7D).

So, with this long winded introduction, I wonder if others think it would be a mistake to buy the Sigma instead of the Canon 70-200? Thoughts? I've seen a bunch of decent photographs taken with the Sigma, but none by accomplished bird photographers.

I have the 120-300 on the nikon side. It takes the sigma teleconverters well, have used the 1.4 and 1.7. It is sharp and color is pretty good. Focusing is on the slow side, especially for bif. Really slows down with the converters. Since I got the 200-400mm I really do not shoot with it any more. I find the 70-200, at least on the nikon side, a much more useful lens- it is on my camera as we speak.
Gary

Thanks, Gary. Do you have the original 120-300 or do you have the new 120-300 OS version? They supposedly improved the new one a lot.

Sorry, I have the older original model. At least for me you could not pry the 70-200 out of my cold dead fingers.
Gary

Ian, I bought the new 120-300 Sigma with OS. I use it on my Nikon D3S and D7000. I also use it with the Sigma 1.4 converter. I really like this lens, especially hide work. AF is pretty good with and without converter. Image quality is fine as well. You can find some more info on my Facebook page. Www.Facebook.com/renenaturepics
if any questions, feel free to ask.
Rene de Heer

Thanks, Rene. The biggest complaint I've heard has been about focus speed for BIF. What's your experience been with and without TC? (I own both the Sigma 1.4 and 2X TCs)

I would say the Sigma AF is fine but is not as quick as for example Nikon. I have not really used it for BIF.
Rene de Heer

I will be paying special attention to this thread because I too am interested in the new 120-300 with OS. Several years ago, I had the Canon 300 2.8 with IS and even with converters the lens delivered fabulous sharpness and the AF speed was excellent. Unlike you though, I do have a 500/f4 but would like to have an alternative for when the action is closer...