Following. same boat, I'm in a closet 2.5x5x8 500w hps a few cfls. Looking to switch to LED to cut on the electric bill to add another room or tents. The closet is a pain the ass and my state is legal so... Also I have AC in the summer and with the door shut it gets too hot I need to run a fan with a scrubber. I know Mars and HGL have been in the game since I started and LEDs sucked. I'm super nervous about spending $500-$1000 and the bud sucks. I used to go by 2700k to flower 4500 to veg. Max watts/area. These leds are way more complex or at least it seems that way. I can't seem to find any straight forward place to start. Same lights to veg and flower, different, use the power controller to turn down etch.
Today's white LED's include the spectrum from a veg light and much of the spectrum from an HPS. It's an "all in one", instead of separates.
The only company I'm aware of that makes separate veg and flower LED's is HLG. Chilled makes "Growcraft" lights and they had separates until late last year; now they're selling white + far red. The white LED covers the entire PAR range and the far red adds some PPFD but it also works synergistically with red to produce more growth than just the extra growth you get from the PPFD from the far red.
PAR = photosynthetically active radiation - the light that plants use in photosythesis
PPFD = photosynthetic photon flux density - the number of photons hitting a given area in a specified time. It's measured in µmol/m2/s or micromols per square meter per second (I abbreviate that as µmol). That's the big number because it tells you how many photons are landing on your plant every second. A good analogy is how much rain is falling in a square meter in one second.
In HPS, MH, CMH (call them "HPS"), input wattage one big metric, lux is the other. With LED's wattage is only a rough guide to how powerful a light is. Also, lux is not used because lux measures only a part of PAR. I've attached a document I wrote about converting lux to PPFD. Check out the picture with the eyeball.
A good rule of thumb for input wattage is 30 to 40 wats/square foot of canopy space. Per above, that's just a rough guide. I grow my plants at 1kµmol± and both of my Growcrafts are 330 watts. At the moment, I'm running grow at 300 watts and the average PPFD on my canopy is 947µmol .
If you're in ambient CO2, cannabis will grow between 64 µmol and 800-1000µmol, roughly speaking. The latter range is called the "light saturation point" and it is a good general guide. Research into light levels and crop quality have shown the cannabis will grow very well in PPFD's at very high levels (in one study, they stopped at 1800µmol) but, in my grows, plants show signs of excess light as they approach 1050µmol.
The amount of light a cannabis plant can use is limited by the grow environment. I've seen grows that can't handle more than 500µmol while others can grow quite well at double that.
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