Originally Posted by Snook
I'd bet it is all very accurate, informative and thank you for posting
it but I don't get it either.. there are things I have a hard time wrapping my brain around. I get red/blue/green and betting i'm doing it wrong, lol. i'll subscribe maybe I can
learn. til I do, i'll keep buying the 1k HPS cheapie I guess. is there a short/simple explanation of all that? red and blue? lol.
See what I wrote above, about why in terms of photosynthesis, red, blue and green don't really matter that much. It's the PAR range (most active light for photosynthesis) irradiance (amount of light striking leaves) as photons (particles of light) that matter the most.
For Cannabis, somewhere in the range of 600 to 1,000 PAR (as PPFD, the amount of PAR photons in a meter squared) is a good goal indoor or greenhouse. Above 1,000 PPFD for more than a few hours is not a good idea, generally, unless the environment is very well controlled.
So your HPS is good in terms of photosynthesis, in fact, it's YPF/PPF ratio is very high (which means per total light output there's more photons that are more effective at driving photosynthesis than for example, an MH).
However, your el' cheapo HPS lacks important wavebands for some photomorphogenesis. For example, it's likely there is more yellow light from your HPS than is good for the plants, as well as more far-red light than is helpful (leads to plant stretch). Around 10% blue light (as total radiant PPF) is a good minimum goal for plant growth lighting.
I hope clears things up a little, if not, let me know and I'll try to help.