The ring light aka ring flash is generally considered to have been invented by Lester A. Dine in 1952 for use in dental photography but today many people ring light for all kinds of photography. A ring light is a circular flash that fits around the lens and its most important characteristic is providing even illumination with few shadows and can be used to photograph people as well although to paraphrase Jaws Chief Brody, “You’re gonna need a bigger light.”
The larger ring lights units used for fashion photography, power is delivered by a power pack that can be battery or AC powered but some, such as Alien Bees 320 Watt-Second ABR800 Ringflash, are constructed like monolights. Within the circular flash unit, there can be one or more flash tubes, each of which can be turned on or off individually. Some ring flashes have focusing aka modeling lamps for helping low-light focusing. In addition to softening shadows when photographing people, the unique way that a ring flash renders light produces a shadowy halo that fashion photographers like to employ.
To photograph butterflies, I typically use a Canon Macro Ring Lite MR-14EX. With ring lights, the flash tube surrounds the optical axis of the lens. For objects close to the camera, the size of the ring flash is significant and so that light hits the subject from many angles in the same way that it does with a lightbank, softening shadows.
If you can’t afford a “real” ring light you can use an attachment such as ExpoImaging’s Ray Flash 2 that was used for this butterfly photograph. When photographing small objects, such as insects, longer—than 50 or 55mm—focal length is a good idea allowing you to fill the frame without getting too close.