I have an older Olympus OM 50mm lens that I'd like to get a matte box for, as I'm going to use it for video on a 550D. However, I can't seem to figure out what the thread diameter is. There are no markings on the lens itself to indicate what diameter. How do I figure this out?
Here's the lens I have. It's the standard 50mm ƒ/1.8 kit lens that came with many Olympus OM lenses in the '80s