So I had posted a while back about running 16 4' t5's in flower, but due to those agromax pure bloom lamps being out of stock at the time I was ready to buy new lighting, I ended up going in another direction. I was going to spend $350 on two 4 lamp 4' ho t5 fixtures and 8 lamps (including four hortilux powerveg UV lamps) anyway, so after some research I picked up a 1000w Galaxy DE ballast, a Solistek 1000w DE 10k Finisher lamp, and a cheap DE wing reflector for $385. The ballast and lamp can run at 750w which is less than the 864w the 16 ho t5's would be pulling, but can also be overdriven to 1150w which some claim provides the best spectrum/impact on plants as a finisher (higher UV output?). This will be an experiment in its own right and I'll be using 432w of 6500k and 3000k t5's i already have to reduce electricity usage/light the tent when I am working nearby because this 10k finisher puts out a lot of UV. Note that there are some threads out there related to running MH lamps in open reflectors being dangerous. While I can't find any evidence of anyone actually being harmed by a MH lamp in an open reflector after light searching (and I used to run a 400w MH that way when I was younger and completely oblivious with no ill effects), I will be taking the precaution of never opening the tent (or really being near it) while the 1000w DE MH is running in the open wing reflector. The open reflector is possibly beneficial due to the UV filtering effects of most glass. This solis tek 10k is made with low-iron glass that doesn't absorb UV and supposedly it will sunburn you in short order.
Anyway in my reading I came across some info that leads me to believe 5000k t5 bulbs could be superior to 6500k for veg due to having the same amount of blue light, less green, and more red. I also learned that standard t5 fluorescents are not at all actually full spectrum lights, they would more accurately be described as tri-spectrum lights as the light they put out is almost entirely in 3 narrow bandwidths. This is because they are using the same three gases in every standard lamp, just in different ratios to get different kelvin temps. Every spectral graph of every standard t5 i can find shows the same pattern of the vast majority of light being emitted at about 440nm blue, 545nm green, and 610nm red. I think this explains why t5's with a high kelvin rating are so effective in veg - the blue light they emit is in the ideal range for blue. This combined with the excellent efficiency of ho t5's makes them perfect for veg. There was a guy on another site saying that buying all 4100k or 5000k lamps was the same or better than mixing 6500k and 3000k because all these t5's emit the same frequencies, simply in different proportions that appear as different colors to the human eye and brain. He was saying that since you want uniform light distribution, its just easier to buy all 4100k or 5000k lamps than mess with mixing lamps unless you have reason to believe a kelvin temp of, say, 4750k (what he calculated the 50/50 mix of 3000k and 6500k to be, not sure if it really works that way) is actually better than 4100k or 5000k.
http://www.tcpi.com/spec-sheets/
(Note that the kelvin temperature on the spec sheet for the 4100 54w T5 model says 3500k, I can only assume it's a typo.)
The above link (go to linear lamps and ballasts) makes it easy to open up spec sheets for the different kelvin temps as tabs in your browser and click through them to compare the graphs. Most graphs from other companies show even more dominance of the three dominant wavelengths and less radiation emitted in other ranges than what is shown in these graphs. What I am seeing is that the percentage of blue light (about 25% or .05 out of .20 in the 3 dominant frequencies) is the same in 6500k and 5000k bulbs - the same amount of blue. The only thing that changes is that green goes from .10 out of .20 to .09 out of .20, and red goes from .05 to .06. More red, less green. This would seem desirable, yes? When you move into the lower kelvin temperatures, the blue becomes a smaller portion of the total light and since blue is the fluoro's bread and butter for growing those compact healthy plants we know and love, this would seem undesirable.
The question I have when it comes to flower is, how good is this 610nm red light for flowering? How much of the growth of buds grown under a mix of 6500k and 3000k lamps is coming from the red and how much from the 440nm blue that is still present even in the 2700k lamps? If the blue is driving growth, how much red does it take to stimulate flowering? It would be interesting to test all 4100k lamps (with a higher percentage of blue and green, and a decent amount of red) vs all 3000k lamps.
Many graphs showing only chlorophyll a and b, or showing individual pigments, seem to treat 610nm red as being nearly useless for plant growth, but other graphs showing overall plant absorption show 610nm red as being in a pretty good part of the red spectrum, or even the very peak. The McCree curve has 610nm at the peak of the graph for "average plant response". It comes from a 1972 academic paper from the journal agricultural meteorology and is often cited by LED manufacturers; it is referenced and linked on the wikipedia page on PAR.
http://plantphys.info/plant_physiology/images/psnpigmentspec.gif
http://www.marigoldlighting.com/wp-content/uploads/2015/03/PAR-Curve.png
http://pinklightaeroponics.net/wp-content/uploads/2014/02/Photosynthesis-Absorption-Spectrum.gif
https://www.google.com/search?q=545nm+wavelength+light&source=lnms&tbm=isch&sa=X&ved=0ahUKEwiu8a25m7TMAhVR4mMKHbEpCJMQ_AUIBygB&biw=1433&bih=748#tbm=isch&q=nm+wavelength+light+plant+absorption&imgrc=LW5TZyGJ4i-8rM:
https://en.wikipedia.org/wiki/Photosynthetically_active_radiation
One thought that came to mind is that the 610nm is slightly higher frequency than the pigment graph's ideal reds that vibrate a little slower. Could it be that the 610nm red slows down slightly as it bounces around in the tent , in the canopy, and in the leaf, thus providing a pretty good usable red spectrum in the process of dissipating into heat? There is some ambiguity about the effectiveness of 610nm red light in driving plant growth, at least for me, because I don't have any experience using all 3000k lamps successfully. Input from anyone with a lot of experience using 2700k and 3000k t5's would be great to illuminate this for me. Do they drive growth on their own or is more blue (higher kelvin temp) better for yields as well as for maintaining healthy plants?
Thoughts?