DIY Ring Flash with a 150-Element Optical Fiber Whip

There are plenty of do-it-yourself ring flash projects around, either sporting any number of white LEDs, or foil-clad tube constructions directing the light from a flash to a ring around the lens. However, state of the art LEDs still produce rather little light, and there's a flexible and perhaps even more efficient alternative to transporting light via a tube fitted with reflective walls: optical fibers.

Optical fibers are specifically made to transport light, so my idea was to construct a ring light based on the same principle as the popular optical fiber lamp: a large number of optical fibers are collected at the light source, leaving the other ends fanning out in a spherical shape. For flash purposes, this light source is of course a regular flash unit, and the other ends of the fiber optics cables are fitted in the circular outline of the ring flash, that is, where other DIY people have placed LEDs. Unlike LED constructions, however, this construction allows the camera to adjust its flash intensity automatically, and it doesn't require a power supply. Also, with a large number of fibers, the light should be very evenly distributed, possibly eliminating the need for a diffuser.

It turned out it was difficult to find suppliers of fiber optical cables in my country. The only supplier I found agreed to cut 150 pieces of fibers (length about 50 cm, ø 1,0 mm each) for me and melt together all the fibers in one end. My reliance on the supplier probably makes my particular solution rather costly compared to what may be expected in other countries. However, it's not necessary to melt the ends together (it simply allows the fibers to absorb more light, yielding a better output), so cutting and bundling the fibers is something anyone can do without professional help. The optical fibers themselves don't seem to be expensive at all.

I tested the light conducting capability of the fiber optics whip by holding the glued end in front of my camera's built-in flash unit and looking at the free ends while firing the flash. Don't do this at home: it worked much better than I had hoped, and was practically the same as looking straight into a flash at close range.

The next part was to construct the ring where the optical fiber ends are attached. I cut the ring from a piece of acrylic glass (you may of course also use wood, cardboard, plastic, or metal) with 150 ø 1,2 mm holes drilled in a uniform pattern. The holes are organized in concentric circles with 36, 37, 38, and 39 holes and slightly rotated to distribute the fiber cable ends as evenly as possible. I used Inkscape to draw a template for the ring. You may download the template here. I created four templates (one for each circle) instead of plotting all holes into a single template, because otherwise the paper would probably crumble before I was even halfway through drilling. I also waited to saw the inner circle and the outline in the acrylic glass until I had drilled all the holes. The uneven edges of the cut were easily smoothed by sanding the plastic.

Next, I inserted all the fiber optic cable ends in the holes and fastened them with superglue. I did this in several rounds to allow the superglue to dry before working on the next bundle of cables. I also fitted the acrylic glass ring with a ring of cardboard so that could it slide snugly onto the lens.

For the other end of the fiber optics cable whip, I created a fixture for the camera's built-in flash by cutting and gluing a small fixture of cardboard that could slide onto the flash in one end and onto the fiber optics whip in the other end, and covered it with aluminum foil inside.

With all fibers and the inner cardboard ring attached (including an unexpected 151st fiber that also happened to be too short and was left dangling) the ring conducts light from a regular desk lamp just nicely:

I used cable strips to bundle the fiber cables together in order to ease its fitting onto the lens. In the end, "The Ram" hardly hardly improves the looks of the camera, but that was kind of an expected trade-off:


In practice, the ring and the fibers block some of the measuring light and probably cause a slight miscalculation of the target flash intensity. However, the resulting light is reasonably well dispersed as illustrated by this snapshot of a nearby cactus flower:


There's probably room for some improvement in the link between the whip and the flash, but all in all I think this experiment illustrates that fiber optic cables can be successfully applied as a ring flash.