Hi, I'm brand new to the Photo Forum and almost as new to photography besides point-and-shoot! As I've been getting into taking pictures, I've dusted off an old Konica Autoreflex TC that once belonged to my great uncle. Among the lenses that dear Uncle Hymie had for the camera is a Vivitar 70-150mm f/3.8. When I use the lens on the Autoreflex in autoexposure mode, the diaphragm will stop down as the exposure is made but then refuses to open back up afterwards, so my viewfinder stays dim. The only way to get it back open is to take the lens off the camera! Everything works properly in manual mode, and the other (Konica Hexanon) lenses I have work fine too. Is something wrong with the Vivitar? Or is it maybe just incompletely compatible with the Konica?