A DIY ring light flash for macro photography, using a Yongnuo YN-560IV flash and a 77mm diameter lens. It is designed to fit around a Nikon 24-120mm f/4 lens, so it may not fit other lenses, even if they take a 77mm filter. Some effort could be made to make it threadable onto a filter ring, which would make it more generic to other 77mm diameter lenses.

Requires 25 ft of TOSLINK cable, probably the cheapest would do, such as this: https://www.amazon.com/Monoprice-Toslink-Digital-Optical-Audio/dp/B003WM2RJK