Foxy Brown
New member
I've read alot of post about LED lights that use a combination of "cool white" and "royal blue", with the CREE XP-G and XP-E being often preferred.
Alot of discussion then pops up about whether LED light can provide the kind of spectrum that corals need. I've also seen a few RGB and even some RGBY lights out on the market that try to provide a better color spectrum for this very reason.
The trouble is what looks good to eye has very little to do with the actual spectrum, because our color sense is terrible. Even actual PAR measurements aren't perfect because a really intense light at only one wavelength (say green for instance) could give excellent par readings, but still not be of much use to corals. So what we really need is some actual spectra.
Lets look at the colored XP-E's
So you can see that even with the commercial R-G-B-Y mix, while it may look white to you and me, the peaks are quite sharp and with some honking big holes in between. Not much like the solar spectrum.
Now, the bandwidths of the white LEDs are much better but still have holes around cyan and red. You can use "warm white" leds, but that just leaves a really big hole in the green (500nm ish). So, why not find a couple more LEDs to fill that in... this is what I got from extracting the spectral data from Cree's datasheets, and adding some selected ones together.
Notice how flat and broad it is, no wavelengths below about 60% of peak (so no holes) and plenty of red intensity even out past 650 nm.
This is a combination of Green, Blue, Royal Blue, and Warm White. Of course, the actual intensities are arbitrary, so I can't be sure of the actual ratios you'd need but it looks like about 1-1-2-3 should give a nice balance, though probably a lot more blue than what is shown here, which is desirable anyway for most folks. Of course, there's no need to run them all at 100%, so it could easily be tweaked.
So what do you think, has anyone tried this combo?
Alot of discussion then pops up about whether LED light can provide the kind of spectrum that corals need. I've also seen a few RGB and even some RGBY lights out on the market that try to provide a better color spectrum for this very reason.
The trouble is what looks good to eye has very little to do with the actual spectrum, because our color sense is terrible. Even actual PAR measurements aren't perfect because a really intense light at only one wavelength (say green for instance) could give excellent par readings, but still not be of much use to corals. So what we really need is some actual spectra.
Lets look at the colored XP-E's
So you can see that even with the commercial R-G-B-Y mix, while it may look white to you and me, the peaks are quite sharp and with some honking big holes in between. Not much like the solar spectrum.
Now, the bandwidths of the white LEDs are much better but still have holes around cyan and red. You can use "warm white" leds, but that just leaves a really big hole in the green (500nm ish). So, why not find a couple more LEDs to fill that in... this is what I got from extracting the spectral data from Cree's datasheets, and adding some selected ones together.
Notice how flat and broad it is, no wavelengths below about 60% of peak (so no holes) and plenty of red intensity even out past 650 nm.
This is a combination of Green, Blue, Royal Blue, and Warm White. Of course, the actual intensities are arbitrary, so I can't be sure of the actual ratios you'd need but it looks like about 1-1-2-3 should give a nice balance, though probably a lot more blue than what is shown here, which is desirable anyway for most folks. Of course, there's no need to run them all at 100%, so it could easily be tweaked.
So what do you think, has anyone tried this combo?
