I just received my O-Flash (which is a cheap e-bay knock-off, similar in design to the RayFlash adapter). I ran a few comparison tests, but they're not ideal (my O-flash is the 179 model, for SB-900 and D300s - which is what I want, but Mr Postman hasn't yet delivered my SB-900, so I had to run the tests with my SB-600 which is physically smaller, so the O-flash didn't fit correctly...)
First impressions are mixed. The black section is very robust feeling, as are the clear light-channelling moulds. However, the clear cover that sits over this is *very* flimsy - similar to the packaging plastic you often get moulded around small items like USB drives or SD cards... Not sure that this will stand up to much abuse, but even if this breaks it shouldn't actually effect the quality of light. Which is the next problem...
I made some test shots to see how much light was lost in the adapter, and the results are below - read it and weep...
First, a 'reference' shot. For ALL of these shots, the camera was in Manual, as was the flash for consistency of exposure. None of these shots have been edited - these are JPGs straight from the camera with no levels/curves or other exposure tweaks in post. I was about 3-feet from Bob The Builder for these shots
ƒ6.3 | 1/100s | ISO400 | Flash @ 1/64 - SB600 on bare on camera
Next, I took the same shot, but this time with the O-Flash adaptor added
ƒ6.3 | 1/100s | ISO400 | Flash @ 1/64 - O-Flash adaptor
Wow - the O-Flash is *really* eating the light! Just to be clear, these two shots (above) were taken with the *same* camera settings and the *same* manual flash settings.
So I adjusted the flash output, keeping the camera exposure consistent:
ƒ6.3 | 1/100s | ISO400 | Flash @ 1/8 - O-Flash adaptor
ƒ6.3 | 1/100s | ISO400 | Flash @ 1/2 - O-Flash adaptor (still under-exposed compared with the bare SB-600 @ 1.64!)
ƒ6.3 | 1/100s | ISO400 | Flash @ 1/1 - O-Flash adaptor (FULL POWER!)
So by my eyes (and nothing more scientific) the O-Flash exposure is slightly under the reference shot at 1/2 flash power, and slightly over the reference shot at 1/1 (full) flash power. Bear in mind that the reference was at 1/64 flash power, that means the O-Flash has lost about 5 1/2 stops of light. Wow. That's gonna cost me in batteries.
But, one thing I noticed when I dismantled the O-Flash (hey, I'm curious - gotta take things apart!) was that the 'reflector' to channel the light from the flash-gun around the ring was plain, matt, textured CARDBOARD! Which, according to my eyes, is NOT reflective. So I figured I'd replace it with my own cardboard copy, but I'd stick aluminium foil to the back to give the light a chance. The original cardboard is on the right, and my homemade copy is on the left.
Lets see if that improves the illumination
ƒ6.3 | 1/100s | ISO400 | Flash @ 1/4 - Modified O-Flash adaptor
ƒ6.3 | 1/100s | ISO400 | Flash @ 1/2 - Modified O-Flash adaptor
ƒ6.3 | 1/100s | ISO400 | Flash @ 1/1 - Modified O-Flash adaptor
This is *slightly* better with the foil added, but still losing a LOT of power...
I'll need to run some more comparison tests, but so far I'm slightly un-impressed...