I just learned about using a reversed 50mm lens for macro photography, and I thought I would try this with the Canon FD 50mm 1:1.4 lens that came with my wife's Canon AE-1 many years ago. I read that it's possible to test the procedure simply by holding the lens in position, but I discovered that once I remove this lens from the AE-1 body, the aperture closes down to approximately f8, and the image I get (though greatly enlarged) is extremely vignetted as a result--all but a small circle at the center of the image is obscured. Turning the f-stop ring has no effect on the aperture opening. Putting the lens back on the AE-1 opens the aperture completely again, but a good half hour of poking and prodding failed to produce any way to open the aperture when the lens is off the camera body. Can I use this lens for reverse-lens macro photography?