I'm almost 100% positive that it will not work with any lens (...)
One cannot just stick an iris in front or in back of a lens and expect it to work like one that's internal.
I guess this goes to show that someone can be a "terrific videographer" and not know #$%@ about optics.
Bif, I'm sure you are right, basically, about where a proper aperture should be. But is that the point?
I'm pretty sure it works with the focal lengths of my interest; the fast 50 to 100mm range. I base this on no theory at all, I know nothing about optics except from what I've learned by experience. I'm confident though that somebody intelligent well versed expert on this forum can explain everything, or at least give us a link to a ton of Zeiss white papers, lol.
I mentioned many have tried to make baffles for their fast 50mm lenses. The only effect that has been seen from all this work has been images that effectively have been looking as the lens has been stopped down.
I don't recall when I last stopped down beyond f/4 or so. Now, if this adapter allows a reasonable result from these fast lenses between say f/1.2 to f/4 matching what these lenses would do if they were internally stopped down, then there is definitely a use for this adapter. No more Zeiss sawtooth bokeh! No more ugly hexa, or octo-, gonals.
OTOH, it may be that Kipon never tried their idea before manufacturing and starting to sell the adapters. Then the incredible video guy is bought buy them and promotes the useless stuff along with a couple of those having commented the product at his site. Nothing is impossible.
EDIT: I didn't see your reply, Diane, before starting to type this. The next generation adapter Phil mentions is the electronic one working as a full flange interface between the Panasonic cameras and the EF lenses. That is cool, but expensive and probably worth it for the hard core video maniacs only. I woul dthink a fully manual lens will be the best one in most of the cases... with a stepless aperture....