a special flash that mounts on the front of your lens and is shaped like a, errr
An independent light that usually connects to the microscope body and gives off a ring of light. Ring lights are generally either fluorescent or halogen and are attached to the bottom part of a stereo microscope, right above the stage where the object rests.
(Vision Sensing) A ring light provides diffused illumination over a small area. With the lens axis through the center opening of the ring light assembly, the ring light illuminates the area directly in front of the camera. Learn more about ring lights here.