Yesterday I got to have a brief look at both the ring flash and the twin-light model for Canon Macro lenses. The latest lens with its 67 mm size needs a step-down ring to fit the flashes. Otherwise, all works OK. I took a small flower into the shop and tried them both out under pretty rough and hurried conditions. Nevertheless, I feel the twin-light set up gave a picture with better definition than the ring flash. Have any of you used both often enough to be able to comment? I feel the twin-light will take a lot more getting used to because it seems somewhat unwieldy, but would be worth the perserverence if it really is a better piece of gear.
As for a flash on the telephoto lens... I have resolved to forget it.