a 600w hid lamp is an inefficient light, that gives off fuck loads of heat.
315w cmh is more of a spectrum like the sun. Much closer to full spectrum than hps. White light basically. Also means you can see your plants properly, unlike under hps.
600w hps draws 660w, 315w cmh draws 340w, so almost double the w, for about the same amount of light. These are under 1 315w cmh, though I did have 2 cmh lamps in there for half the grow. These are 7 1/2 weeks from seed here. Sweet cheese's.
Many say the plants grow faster under cmh, due to the wide spectrum.
Also the quality and smell is better than hps, as it is with led too. Led grown bud is very similar to cmh.
Imagine having a lamp that runs 10% hotter than a 250w lamp, that covers 1m x 1m minimum. I use them in 4ft x 4ft areas.
do have 315w cmh 4200 daylight lamps too, also the 3100k agro lamps.
Hps spectrum is pretty crap compared to cmh, especially with the daylight lamp. I hit over 1 gram per watt with the daylight lamp, in 8 weeks from seed with auto's. Only time I've ever got 1 gram per watt. You can have these lamps 1ft from the tops, though 3ft is a good distance, mainly coz you get the perfect environment. Running 2 315w cmh unit side by side, 1ft from the canopy is far, far better than a 600w hps at 12''-18''. I intent to run 630w cmh still, howver it doesn;t change the fact that a single 315w cmh lamp is brilliant to use and a pleasure to grow under.
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