I suppose that depends in part on how close you can get.  I read somewhere that local regulations in that part of the world precluded you from getting within (even tele) reasonable photo range - as soon as you saw a PB, you had to start moving in the opposite direction - but I might be wrong, or have the wrong geography.

I've had good luck with the 300 2.8 and the tc's.  Even stacked the results are acceptable, and you'll still have AF at F8 on the DS.  

Here is a link to some samples I shot from the 70-200 100-400 and 300 with various combinations of TCs

PB's are on my list - but I'm looking at Churchill Manitoba as a reasonable location.

Hello,

in summer I´m going to Spitsbergen to shoot
polar bears. I use the new Canon 1ds II - and
am thinking of buying a super tele for it -
I just have a 100-400 and 70-200 (both IS and L)
and the two extenders (1.4 / 2.0).

So can anyone with close experience recommend
me a lens? I am considering the three lenses
(but of course only one can be bought!) -
the 2.8/300, the 2.8/400 and the 4/500.

I am tending towards the 400 but its very heavy
and the most expensive one.

any suggestions?

Thank you very much,

Andreas.
Concorde-SST
www.suchert.com

Hello Tim,

thanks - I forgot to mention that I´ll shoot the polar
bears from a ship or from a Zodiac. I´m on a Van Os
Photo Safari - usually I don´t like tours very much
but given this destination there is no other way.

So I guess I´ll come pretty close to the bears - very
good example shots you made - thank you!

I guess I have to try - for distance the 400 will do
the trick...hmm...have to see...

all the best,

Andreas.
Concorde-SST
www.suchert.com