Just bought a Soligor 75-205 zoom lens for my Canon Ae-1P. The shutter-mirror doesn't fully expose when this lens is attached, unless I push in the "stop-down lever." I can also take photos with the stop-down lever engaged but in the manual it states that when shooting with the lever engaged the exposure may not be correct. For those who are unfamiliar, the stop-down lever is used for metering. Here is a picture of the lens mount, and a picture of my 28mm vivitar lens with a proper FD mount: (above) Soligor 75-205mm with funky FD mount. (below)Vivitar 28mm FD mount.