I currently use the Canon 400 f5.6L and 100-400mm L lenses with a 30D but would like more reach. Whilst I would love the 500 F4 L it is just too much cash to lay out. The Sigma 500 F4.5 EX APO HSM can be found for approx £1500 2nd hand. Is this a decent compromise?
Thanks
Rhod
PS will the Sigma take a 1.4x extender?
I bought one secondhand last year as an upgrade from the bigma. Very happy with it too! It is a big lump to carry around, though, and I have found my birding photography is much more tripod-based than it used to be. I can hand-hold the lens, but not for very long stretches. If you look in my gallery for images after September 07, they'll be taken with this lens (and in Postcardcv's gallery before then it'll be the same one - I bought it from him!)
I was in the same position but in my case it was Nikon. Image quality is "probably" a bit less then the "proper" lenses, but I will probably stick with the Sigma now that I have it. It is heavy, but manageable - I often use it with a monopod, and in a hide can easity be hand held. Not sure a Nikon or Canon 500mm f4 would be as easy.
For a 500mm prime lens it is fairly compact - and that is where it wins.