Thanks for all the replys.
I'm still trying to make my mind up. I'm wondering has anyone tried the Sigma 120 - 300mm f/2.8 lens on the 5d mk 3. (sorry to say the "S" word on the Canon website)
I think if I used the 1.4 Tel converter it would make it a 120-300mm f/2.8 lens as a 168- 420mm f/4 lens.
A 420mm f4 would be epic (is this a possibility, has any one tried this???)
Can you use the canon 1.4 on a s Sigma lens??
I do. I contemplated purchasing the Canon 300mm f/2.8L II however ended up opting for the Sigma 120-300. I absolutely love the lens (although it is a heavy beast). I also have the Sigma 1.4 TC- There is a slight noticeable drop in contrast and a little bit more noise when using the TC, but the images are still superb.
I will see if I can get a few pictures up for for you.