Canon 300 f2.8 L IS USM v. Sigma 300 f2.8 EX DG HSM

Added the 300 f4 IS, 200 f2.8 L II, and 70-200 f2.8 IS into the mix http://www.pbase.com/l​ightrules/300speed3

I am from the UK and really a beginner with a DSLR perhaps a year. I am really interested in this thread as I have a cannon 300mm 2.8 IS lens, I got it seconded hand in as new condition. I have used it with a 400D and 40D with results I am pretty pleased with on its own and with a 1.4 extender. I have also tried it on a 1D mark 2N on which I am disapointed with (the camera) I will try again as I got the 1D for in flight action shots. As a beginner when I brought my first L lens the 100mm - 400mm 5.6 IS and thought it would perform like the hubble telescope. After the intial dissapointed that it did not bring small and medium birds to fill the frame from several yards away. I soon found its niche and I have to say I really got to like it and its a keeper for me.
Again the 300mm as served me well with the little time I have been using it. And here comes my question will the 300mm work well with the1.4 converter plus a 2X or even two 2X giving 1200mm @ 11.2 if I have worked it out right.
The reason being trying to get that little bit closer to flying peregrine falcons coming and leaving their breeding area. Heres a couple taken with 300mm plus 1.4 converter on a dull day at the local park. Plus please as anyone got any birding shots with the 300mm lens with stacked converters that they could post.
Regards
Colin

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Just for a laff I tried a 300 with stacked 1.4 and 2x converters on a 50D. AF was pretty poor, not even finding the subject most of the time (although the light was terrible). When it did lock on the image quality wasn't as bad as I was expecting (but I was expecting it to be terrible). I also tried adding a 1.5x to the stack (a total of 2016 mm, inc crop factor). Wouldn't AF on anything at all.

Unfortunately I deleted all the images (I think, I'll check when I get home).

Nice tree shark.

Lighty, my boy, so glad you're back reviewing stuff. You be da man. And the best in my book.

Now, about that 6.5 fps thread.
me

Snir, how you likin that 200-400? It was a hard decision between that and the 300 VR for me, but I'm living the 200-400.

jojo, dang you...
I appreciate the test! Maybe next year I'll hock my 120-300 for the 300 2.8 IS...