I have bought 5 different OM adapters all at the low end of price. In all but one case the piece that holds the Aperture pin open does not open it far enough so that when you stop down past 8 or 11 it will not go further.
I have tried two Fotodiox, a cowboy studio, FOTEGA and a FOTASY. The FOTASY was the only one that caught the aperture correctly.
Has anyone else experienced this? Am I missing something?