Ring light 3.0: CCFL Ring Light
Note from the author: my ring light pages have had hundreds of thousands of visits since I started writing them back in 2005. Fuzzcraft has been stampeded by StumbleUpon, has starred on Hackaday and DIYphotography, and is constantly being linked to from flickr, strobist and other blogs, forums, etc. I thank you all. It's nice to have done something that appeals to so many people.
There's something magical about ringlights. The unnatural light cast, the halo shadows. Yet the idea behind them is as clever as it is simple: looking through the light source.
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A ring light with LEDs is all nice and stuff, and it's really bright with 140 of 'em, but the color temperature (around 9,500K) is not well suited for use with any other light source, and correcting the strong blue cast is nearly impossible, because there are no balancing filters available for this. The light from CCFL tubes is much more like daylight (I'm guessing 5,000K), so it can be more easily combined with other light sources. However, incandescent (2,500 - 3,500K) is still out of the question, because the difference is still way too much to not get yellow-orange casts. Daylight corrected incandescants are the proper way to go about this. Or you could use daylight correction filters on normal incandescants to get nearly the same result.
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The trouble with CCFLs is that they're usually straight, L-shaped or U-shaped. Ring shaped ones only come in colours, for use in computer case modifications (CCFL fans), not white. So I thought. I spent many, many hours looking for white, ring shaped CCFL tubes, and finally I found them at a WilTec, a German car tuning shop that sells them as alternatives for "Angel Eyes". You know, those light-up headlight rims on BMWs and other high class cars. They were pretty cheap, so I ordered a bunch. They come in 4 sizes: 40mm, 80mm, 100mm, and 130mm. I decided I wanted about the same light output as the LED ring, so I arbitrarily set the target of 4 rings. 40mm is too small, 130mm is too large, so I settled for 2 of each of the 80mm and 100mm rings. Please note: this shop is one of the very, very few worldwide who sell white ring CCFLs.
Now all that's left is to attach them to a camera lens barrel. Thus began the search for a suitable reflector cup. I could've gone the easy route and made it out of cardboard and tin foil, but that wouldn't hold up to heavy use and moisture, so I decided to do it properly the first time. I looked at different lids for glass jars. I also came across a lid for a toilet brush holder, nicely chromium plated, but I'm just not sure about buying the whole darn thing just to use only the lid. Another possibility is to machine an MDF ring with a plunge router and a rounded router bit, then painting the inside with silver paint or inlay a reflective metal foil. This would be light, sturdy and exactly tailormade, but a lot of work. I also briefly considered plastic modeling mass (Fimo), but I'm not sure how sturdy this stuff is.
To cut a long story short: I decided to go the MDF route (pun, hehe). I took a 1" thick piece of MDF and routed two 12 mm slots in it. The center diameters are 76 mm and 96 mm. So the 2 slots actually overlap and the result is a 22 mm wide slot with a W-shaped bottom. Then I cut out the outline at 126 mm.
It's not the best routing job I ever did, but I'll sand it down a bit so it'll be smooth. The problem was my
router compass. It's made of plastic and has way too much play for this kind of precision work. I should make a metal one next time I try something like this.
4. I did another 2 routing passes to separate the center and a sanding job and this is what the rough MDF part looks like
I decided not to trash another filter to get a filter rim. Instead I made the ring fit onto one of the lens adapters I have. The adapter fits very snugly so it doesn't even need fixing to stay in place.
5. The next step was to paint the inside pearl silver so it'll reflect a large portion of the light forward. And in order to keep the ring itself out of image reflections as much as possible I painted it matte black:
But this is where I got stuck. The CCFL tubes provide a heckuvalot of light; easily twice as much as 140 LEDs. But the ring reflector isn't doing a very good job in aiming all that light at the subject. There's hardly any light fallof for large framings, but that's not what I was going to use this ring light for. For portraits and such there's still too little light. I guess I could attach a hood of some kind to narrow the beam, but a 12.5 cm diameter 30 cm long tube would be very impractical to carry around, and would still scare small creatures away. So until I come up with a better idea (or perhaps a clever idea for a ring flash), this project goes in the fridge. Not every project on this site is as big a success as I would like it to be . I could show you the example photos, but they were so disappointing, I'd rather not.
Continue reading about ring lights: Ring light 3.1