Close up lenses (diopter lenses)

I once saw a trick for doing closeups that should work for diopters. It was to rig an alligator clip on an assembly that would screw into the tripod mount. The distance and position is set just right for using a specific diopter and image location on the film plane. You clip the subject (perhaps a flower) in the alligator clip, and you don't even need a tripod, or at least so they say. You would probably need to stop down to be sure your subject is in focus, but you are going to want to do that anyway.

By the way, I would like to find a +1/4 diopter that I could screw into some of my long focus lenses. I have a 180mm Sonnar and a 150mm Kalinar for medium format cameras. They don't focus quite close enough to do the portraiture framing I would like, but with a very weak diopter it should be just the ticket for this application.

A 1/4 diopter would be just right for most indoor shooting because you could focus anything between 13 feet to probably around 4 or 5 feet, maybe even a little less.