I think the * 60-250mm is a FF design, according to its patent. But it has that back baffle. There were threads about removing it, but I have not seen any sample photos with before/after, so that we could tell what exactly happened. Maybe now that K-1 is out more people would have incentive to try this. Maybe someone can even offer this mod as a service, maybe even Pentax themselves. It certainly seems like a good lens, and if a small modification can make it perform better on K-1, why not. Its a "at your own risk" type of thing, though
Originally posted by JimmyDranox For comparison, remember that almost any lens is sharper not at it's bigger opening, but when you close it about two stops.
You're saying that ring acts as an aperture? Its possible, but only for wide open. Wouldn't the aperture blades be the actual aperture on all f-stops except wide open?
So yeah, this might affect performance wide open, increasing image circle diameter, possibly increasing aperture (very interesting idea), and softening the image. I think the main issue would be lower contrast, as less light might get absorbed by the felt, so it could continue to bounce around the mirror box.