Ring Flash Week: Designing the HD Ring Flash
I have been pining for a good DIY ring flash adapter that will do everything I want it to do for a year now. Every time a new design would pop up, I would want to play with it. But ultimately, I knew I would be disappointed if it would not meet my needs. So I just let the idea sit in my head and percolate a little longer.
The result is the Strobist HD Ring Flash Adapter. The "HD" stands for "Home Depot," because that's where all of the parts came from.
(More after the jump.)
Design objectives, in no particular order:
• Speedlight Based
Sure, I could drop $400 on an ABR800. They are great units, and will do everything I need. But I already own the light output. All paid for. So it seemed kinda wasteful to just go and buy my way out of my problems. So I wanted it to run on speedlights.
Besides, that would mean I could go TTL if I wanted to. (Hey, I do that sometimes...)
• Strong Enough to Use Outside
Almost every DIY setup to date failed on this one. I realized pretty early I would want two speedlights driving it, fired directly at a front diffuser.
• Even Light Around the Ring
Here was the other factor that led to two speedlights. Every one-flash design I have seen balances light even-ness with output efficiency. I needed both. I needed two, symmetrically placed speedlights.
• A Large Ring Source
I like the soft box / ring flash look. Besides, if I want tight and sharp ring light I can always mask it. Not so the reverse with small designs.
• Reasonably Inexpensive
For me, that means $50. Otherwise, what's the point? Just go buy the ABR800.
• Reasonably Rugged
Why bother to design and build it if it would not last? I love some of the folding designs that fit in the camera bags, but they fail on criteria 2, 3 and 4. So I was committed to building something a little more substantial.
• Reasonably Portable
This, I was willing to bend on. In the end, I settle for hand-holdable. I will be putting a 1/4x20 mount on it soon, tho. Monopod and ball head would be a perfect support.
Eventually, I settled on a donut-shaped device which basically housed the camera itself and two lights. I designed it around a specific camera, the D70s, because of it's awesome sync hack. But you could use this reasonably close in full daylight with any camera that synched at, say, a 250th.
Given that the measurements are based on a camera a specific lens, I designed it around a Sigma 50-150/2.8. [Nikon|Canon] I love this little lens -- fast, sharp, light, reasonably priced.
(Any tele/portrait lens you can stick in a 4" piece of PVC should be design-capable, tho.)
The heart of the design is a 4" PVC tube: Cheap, strong, cuttable and readily available. The camera mounts to it via a ghetto bracket made out of aluminum plate strip: 1" x 1/8" x 3'.
Didn't even cut it with a saw, either. Just bent it in a vice and snapped it. Very easy. Also made the bends by holding it in a vise and doing it by hand. No machine shop tools were used in the project. Just a drill, a jigsaw, and a vice. A little sandpaper, too.
The PVC assembly was joined to an outer shell made of concrete footer tube. (Mine was 16" in diameter.) That stuff is tough. If you drill holes in it, it mounts very solidly with nuts, bolts and washers.
To the front was fastened a piece of sanded 1/8" Plexiglass. It was "washer" shaped, and I simply traced the inner and outer circles with a Sharpie and cut it with a jigsaw. I sanded the Plexi to make it frosted (both sides) but that was not enough. I also used a sheet of parchment paper on the inside as an auxiliary diffuser.
Also, it turns out I suck at cutting Plexi, so mine had a few non-fatal cracks and was laminated with clear packing tape. I mounted the Plexi to both tubes using "L" brackets.
Here is a drawing that shows the relationship between the flashes and the unit. You can tell where the efficiency comes from. Those two speedlights are both blasting right into the frosted Plexi/paper sandwich.
With the W/A diffusers on the flash and some foil-backed tape, I got nice, even light at the front.
The flashes are held to the insides by good 'ol ball bungees. Love those things.
NEXT: How to Build the DIY HD Ring Flash