So in Part I, we learned why I thought the Orbis flash bagel was for Klowns, and in Part II we learned how I de-klowned it.

Still unanswered: Why would I, an impecunious and not-very-gear-oriented photographer, want to spend $250 on a fairly specialized lighting gizmo that I myself had to finish?

The short answer: It’s David Hobby’s fault.

For those who have not dared face the frightening truth, Hobby is the sinister high priest of the Cult of Strobist, an international conspiracy the goal of which is to convert camera users into what Hobby calls lighting photographers — a concept which I, as more of a subject photographer, find in itself menacing and surreal.

Just as terrifying, Hobby is one of the Blogsmen of the Plugocalypse, that band of photo-industry Nazgul whose fell design it is to lead unsuspecting photographers to covet equipment, books, DVDs, workshops and so forth.

Still, even Nazgul have their plus points (Tolkien’s originals, for example, were impressively skilled equestrians and had excellent taste in jewelry) and so it’s often worth daring to enter the Nexus of Evil that is Hobby’s Strobist website in the hope of gleaning nuggets of knowledge therein. And it was there, in a flash-bagel comparison test, that I picked up the concept of a ringlight as on-axis fill.

The idea is that you use another flash unit, positioned off the camera, as your key light – one that defines the volume and texture of your subject by creating shadows. Then, to keep the shadows from being too dark, you fill them in to taste with a blast from the ring light. Since the ring light is around the lens, it doesn’t create any visible shadows; the light seems to come “from nowhere.” (Unless, that is, you get the subject too close to the background, in which case you get a ringlight-signature “halo” shadow of the sort that might be familiar from edgy ’90s fashion photos.)

Not having any edgy ’90s fashion models handy, I decided to test the on-axis fill principle by setting up this goofy test scene. It doesn’t really need a lighting diagram, because you can see the key light: It’s a Nikon SB-600, lying on top of the bookcase, aimed at the framed picture on the wall. Using Nikon’s CLS flash control, I set this key light to deliver normal exposure as determined by the camera’s TTL flash metering system.

The photos in the gallery differ only in how much fill light I applied with the ring light. I varied it from -3 stops to +2 stops with the CLS control. As you can see by stepping through the images, this creates a range of different looks, from deeply shadowed and dramatic to fairly even. (Click any image to see them larger, with explanatory captions.)

Sure, I could have created the same type of fill effect by bouncing off the ceiling, walls, etc. But that would have taken more flash units, more stands, and more power. The advantage of using the ring light for on-axis fill is that thanks to its compact, concentrated power, it gives a lot of fill control without needing a lot of equipment.

How does it work for real pictures? See part IV for an in-use report!