Originally posted by m8o On this, I'll beg to differ. I've got 100's of shots proving you can very effectively. I can go hours on and off with my left hand holding my right arm with the lens over my left elbow. It does get more challenging with TCs and I usually move to a monopod then.
You are a though character. I own one of these lenses along with the teleconverters--both a 1.4L and a 2x L. I agree with all the comments here that it does nice work.
I have a couple observations.
1) I'm far to shaky to hold it very steady.
2) It is HEAVY
3) I think an F2.8 is sort of pointless UNLESS you are going to use a converter
4) it works well with either converter (but the dedicated converters cannot be stacked) though conceptually you CAN stack an nnL one of these L converters with a generic converter or the Pentax 1.7x adapter. (no promises about the optical result---but physically they will fit. Two type L converters cannot be stacked because the front element protudes into the rear of the lens
5) This lens usually has been selling for less than $2000 on Ebay second hand --in the US.
6) I am seriously considering buying a new SDM lens for taking photos at 300mm, and big bertha just for use with an extender.
7) depth of field is an issue with an extender even at 4 or 500 feet away and I've messed up a lot of photos due to focus failures, because with a deer or elk is usually less than the animal and I tend to fail to decide which part of the animal I want in focus.