we need this adapter for EF lens on the F3

http://philipbloom.net/2010/12/17/ne-adaptor-for-using-you-canon-eos-lenses-on-gh1-gh2-af101/

An adpater that has its own iris blades built into the adapter? I'm curious if any lens experts think that moving the iris plane from the lens' natural iris plane to the adapter instead, will have any ill effects. Doesn't the plane of the iris need to stay exactly where it is in relation to the other lens elements?

Most report some vignetting with these adapters and limited useable "iris" range as a result. The aperture is in the wrong place in the optical path so it doesn't work as well as it should.