I have the Pentax 6x7 with a 90 f2.8 LS lens. I haven't used that feature in a long time but remember you have to cock the shutter with it on "U" to function properly. There's also a cable release socket you screw the cable release into. It doesn't work. With the U/S lever set to U and shutter cocked the cable release should trip the lens but it doesn't. Have a missed something here?What's that socket for anyway? The 165 f4 LS lens doesn't have one.