There is one thing I do not fully understand why you wants to make a white light through RGB part. I understand the theoretical things but have some conciderations:
1) A white light which is NOT composed of (almost)all wavelengths (like it is from a MHI, sun, a very good phosphorus coated led with high CRI), is only fooling the eye. If you in the tank(and you will have) illuminated with RGB-white light have colors outside these three wavelengths(RGB), these colors will not be correct displayed to your eyes. For instance a yellow tang can impossible be yellow as the light lack the yellow wavelength! The light itself can look yellow from RGB if you have a certain ratio between RGB, but still the reflected light from the yellow object can never be yellow! The color we see is a reflection of wavelengths-content, so the yellow fish will in RGB-white light be something else, probably more orange. So the CRI of the RGB light is bad. Do we think that is good? Isn't the goal to have a reef looking for what it is?...and that leads me to the second concideration
2) The fluorescens is as Lasse says not visible when we have yellow wavelength in the light. But what is the problem with that? In nature we do not see the fluorescence of that reason, as sun contains a lot of this yellow as we know. I do not understand why "we" wants to induce an unnatural look? Ofcours we can induce fluorescence, that is not difficult. Just put 100% on blue channel and dim down the yellowcontaining( read white led)...but why? I can not see this as an argument for skipping white diods.
I can see benefits with including some white diods of 2 reasons
1) We increase the CRI, as we induce yellow AND actually all wavelengths between blue and yellow, including a lot of blue. We use the physical law that blue light+ yellow light=white to the eyes. If we to this add some more selective channels like blue but most important red(as the is lacking in white leds) , we have actually a CRI near 100%, and a very natural MHI-like light. I think most producer think in that way, as there is hardly no light´s out there anymore with only the RGB-thinkning.
2) The phosphorus coated white diods are improving an itself getting higher and higher cri. And we can keep the yellow tang yellow and not orange.
The light have not only the biological effect, that is easy, we know exact the absorption of chlorophyll a and c, and some other pigments...but it also have the estetical effect to correct show you the true color, and there the RGB is not a good choice, unless you complement it with more channels...but then we are not taking to RGB anymore, AND besides that, it is difficult as far as I have understood to construct diods with narrow yellow spectra. Maybe that is the reason why the RGB-fixture I have heard about incorporated amber and not yellow??
I can admit that MY light have too many white diods, so according to my opinion they have gone too far. I can not run these 4 white diods/cluster at 100%, and therefore looses quite much of the total effect from the lamp. I would like to have a light with more economical distribution, with the efforts on the photosynthesis, and the some small adding of white leds to get the correct CRI.
With this said, I think you thoughts and experiments with far red is very interesting, and inspiring, and also like the way your aquarium looks like...very natural, despite the RGB;-).....
/Jonas Roman
