Well, I made a lot of extra tests. I have read many documents relating LEDs, color, brightness, bins, CRI, color spectrum etc. All very difficult terms to understand and thereafter to make choices.Chris S. wrote:Sounds like an excellent choice--elegant, and potentially a nice step forward that the rest of us can copy. I enthusiastically look forward to your reports.
I did a test with my existing 6-channel LED version. LEDs were types with 5000 K and a CRI above 90. I took out of the diffuser in the first test and set the WB via the D7100 as preset1. I put the gray card, the Mit 5X lens + the 200mm macro tube lens and take a picture. Via View-NX-i all the information is available. After this test I put the normal diffuser into my unit and take a second picture with the same P1 preset into the D7100. Due to the duffuser, the WB is no more correct, colors are shifted. Lets see an overview:
The camera has a color temp of 4646 K (WB without diffuser as P1). Using now the same preset with the diffuser you have to increase the brightness to have the same exposure. The flash time goes from 700 to 2400 usec, the blue channel has less light, the red more. The picture is no more the gray value.
To have an idee how much change there was, I have done a new WB with the diffuser included and store into the camera as preset P2. lets now look at this picture:
The color temp is now 3609 K and the flashtime 2550 usec to have the same brightness. After this WB, ballans is again perfect with the diffuser. My conclusion is that the color temperature shifts downward. What remains of the CRI value, I can not really measure. Everything is very relative and the question is whether you need the very expensive versions.
My proposal to use two color temperatures will be totally wrong. As long as you simultaneously using only one kind of group it will works, but no more if you change selectieve the 10 channels. The WB will by wrong.
Just now I prefer the 4000 K versions with a min CRI 90 : CXA1830-0000-000N0US240H 4000 K 2780 lm.
http://www.mouser.be/ProductDetail/Cree ... 1gtA%3d%3d
They are also less expensive.