yoni perlmutter , Apr 02, 2006; 02:57 p.m.
The 500D is a double achromat of very high quality.
It is 77mm and can be used on larger and smaller diameter lenses by means of step-up or step-down rings - an inexpensive adjunct. I use mine to good effect on my 75-300, 80-200 and 300mm lenses. I'm sure it would work well on your 70-200.
I have happened in the past to have used it also with the 24-120 and have gotten very good results but I usually keep this to myself because this is a lens many do not regard highly and I'm always "justifying" my continued use of it.
It's a good piece of kit and yeilds good results. Understand though that it is quite a heavy chunk of glass and prepare for it's tripod/balance accordingly.
Focusing to infinity is out, I'm afraid.