Strobist just put up a review of the ExpoImaging Ray Flash. The $300 unit, which attaches to the business end of an on-camera speedlight, looks very similar to my own homemade ring flash. Of course, I can't claim my DIY flash is a unique idea or nearly as good as this product.
From the product page, the secret of the light distribution is:
"...a sophisticated system of internal prisms, reflectors and light-shapers designed to distribute and project the light evenly around the lens..."Well, darn, I guess I should have me some internal prisms.
Ok, ok. It may seem like I'm poking fun at the product, but I'm not... I'm poking fun at the price. $300? Really? 300 is the number in the Spartan elite guard, not the number of dollars you need for a passive flash modifier! You can't tell me that it can't be made for cheaper.
On the bright side, I think there's a lot of room for the price to come down once they reduce manufacturing costs. Or, maybe some Chinese company will steal the idea and sell it on eBay for $50.
Actually, from Hobby's description, it sounds near identical to my design:
"Speaking of engineering, this is a pretty impressive piece of optical design. It uses little light channels to guide the flash around the lens pretty darn evenly. Given that the top is closer to the flash, you know that is gonna be the hot area. But they counter it by not releasing the light fully until they are an inch or two from the top of the ring, going around. Seems to work great."Releasing the light about a third of the way down the tube was one of my ideas to even out the light distribution. But, losing only a stop of light (or half the light energy) is really, really efficient.
The biggest drawback of DIY models like mine is that they eat so much light (I estimated a loss of 4-5 stops, although I suspect a stop or two of that is due to the office paper diffuser). When you lose 95% of the light, that doesn't leave much left over for lighting, especially outdoors. Obviously, there's something else going on here, and it'd be great if Mr. Strobist could help us DIYers reverse engineer the secret to maintaining such high output. Reverse engineering the product would probably go against whatever agreement got him an evaluation unit in the first place though.
Realistically, I won't be buying one of these things. If I have an extra $300, I'll buy a real macro lens or some studio lights, not a flash modifier. Sure, the extra output would allow me to actually use ring light for outdoor shots of things larger than a flower, but the price-performance ratio just isn't worth it to me.
That doesn't mean I wouldn't be willing to evaluate and review a unit for free, though... (hint, hint)