Thanks for the quick reply Andrew . what is the whole deal with Olympus saying that is should be used with f/2.8 lenses .Its hard enough to find Four Thirds lenses, so I would have thought they would be glad to say it could be used with other f/ lenses . Do you know if they are any draw backs at all. I see you have a 70-300 is it a f/4.0-5.6