"but it is in black and white.
metal halide for veg,
hps for flower"
Almost every professional production greenhouse disagrees with you, at least the ones I've been in from Morocco to Australia.
Even the company making Sativex uses PURE MH all the way through for cultivating their cannabis. Why? The company doesn't like etiolation (most commercial operations hate it,) and green wavelengths interfere with the production of THC. This I have noticed as well. Plants under
led are way more potent than the same strain grown under HPS.
"20 hours for veg"
Very few places on the planet even get that amount of light and the best cellular division rates occur after 5 hours of darkness, while the majority of
nutrient transport happens.