[Scooterman]

Craig, in layman's terms, you hit it right on the head.
Please remember, these are some thoughts, I stand to be corrected.
I've studied light years ago, it's effects and absorption is one thing that can get tricky. There is so much information on lighting, that I myself haven't studied on that level but understand what is going on. I agree with Boomer and the PAR for aquarium use is very important, the higher PAR the deeper penetrating or radiation ability of light,. Now with that said, Kelvin, is light measured in temperature, this affects color. All matter either absorbs light or reflects it, white light holds ALL of the colors in the spectrum, black colors are just the opposite, pigmentation of matter will determine how much light is absorbed or reflected. First of all you have to reach corals, so PAR rating is that, intensity of the actual light spectrum being lumens. This ability to penetrate water is what we look for in PAR. I may be corrected on this point but Kelvin in my thoughts of light is varied in reef lighting because one, our viewing prospective & two some level I have to believe that corals absorb light differently at different Kelvin levels, no two are alike, no two are feed the same either. If your looking for best growth, from what I've read 6.5k range will cover all of your corals needs but looks yellowish or crappy in my opinion. This is one subject, I love to read about and at the same time tend to keep commits short, there is too much to cover without causing a major controversy.