How are you planning on using the ringlight? Does it need to be flash? Can it be an incandescent light source? The reason that I am asking is that for some close-up and macro work I have incandescent light sources with fiber optic bundles including a ring light. But these are designed in part for work with microscopes. I have a battery of macro and close-up lenses that can be mounted on several bellows for my Leica R series cameras. They can also with adapters be put into a #1 shutter for mounting on my Linhof Technikardan 45S. The Fiber optic ring light can be affixed to the lenses with adapters or locked in place with clamps. But, I do not think the ring light would accept a 77mm thread (too large). Of the macro lenses that I have they include the Schneider f4.0 50mm M Componon and the Rodenstock f4.0 75mm 1X Apo Rodagon D and the Rodenstock f4.5 75mm 2X Apo Rodagon D lenses. Just some food for thought.