Been reading alot about this and experienced it recently with a Canon FD 50mm f1.8. With the adapter the aperture blades are fixed wide open. There is nothing wrong with the lens as it works on a 35mm cam. So I fiddled with it. I attached the lens to my E-PL1 via the adapter. Once the adapter clicks into place it is fixed wide open. However I uncrewed the lens slightly counter-clockwise from the locked position. The lens is a tight fit onto the adapter so no danger of the lens dropping off. Bingo. The aperture blades then responded to me moving the ring on the lens- but only over a certain range. I then unscrewed the lens a bit further, the range changed but the aperture blades again responded. So I am now able to use the lens from wide-open to stopped-down. Can't judge precisely what the f-stop is but can guess. Works a treat. Not sure why but it does.