I have the 300mm f/2.8L, with 7D and both extenders, and I don't think the 300mm provides enough reach for small birds, and the 2x extender is not that good in my opinion. I shoot mainly sports so my combination works great for me. The 400mm f/2.8L is also more expensive than the 500mm f/4L.


I would strongly suggest considering the 500mm lens, especially since you already own the 300mm f/4L. I understand that the 300mm f/2.8L is much better than the 300mm f/4L, but I don't think it's worth spending $4500 now and then down the line upgrading to the 500mm f/4L for $6000.


For your type of shooting; I would rather have the 50D = $950 and the 500mm f/4L for $6100: total=$7050


instead of the 7D for $1540 and the 300mm f/2.8L for $4500: total= $6040.


or maybe keep the 40D a little longer until you can save up for the 7D and then buy the 500mm /f4L now.





Rich