Quote Originally Posted by Roger Cole View Post
Some cameras have a shutter that can be moved in and out of place via a small lever on the camera body. The AE Prism finder on my Mamiya 645 Pro has this. The only use I'm aware of for it, though, is when using automatic exposure shooting off a tripod, and on a tripod I use manual settings almost exclusively. I don't think I've ever actually used one of these, of either type. Just goes to show - one person's "I have them but have never used them" is another's "must have."
Some cameras came with a little widget that clipped over the eyepice.

When I use my old Nikons, if I'm using the internal meter with the camera on a tripod I just hold my left thumb on the eyepiece while setting the camera.