CMH beat standard MH & HPS in CRI (color rendering index), efficacy (lumens/W of input), and they have greater lifespan than both. They also emit UV-B which has 'anecdotal approval' (if you will) from many growers, but is also largely nullified with thick glass hoods meant for keeping heat manageable. Their overall increased efficiency means a more manageable thermal setup, which can mean a big difference in cooling costs, and happy plants with cool leaves tend to grow well.
And CMH can be run thru the entire grow as well. No need for switching bulbs and ballasts out if you only have one tent. I believe there may be a couple spectrum options with CMH, mid 3000's and low 4000's I believe, but not sure about that, so don't quote me on that.
I don't know however if the advantages CMH holds are enough to make up the difference in raw 'horsepower' a 1000W HPS or MH has over a 630W CMH, but definitely, if you put them up against eachother watt for watt at a 1:1 ratio, then CMH should destroy them both assuming all other things (medium, temps/humidity, feed schedule etc) being equal.
And I can't speak on vertical vs horizontal, all my friends that use them all use horizontal setups, so nothing to compare, so I'd just be talking shit otherwise lol.
MH & HPS are industrial lighting designed back in the 50's and 60's, meant for street lamps and factory floors. Neither were initially intended for indoor horticulture.
CMH were perfected for wide spread use in the mid 80's or 90's I believe, with film and television, photography, and other industries in mind that required a more accurate daylight spectrum. Luckily for growers, plants have evolved demanding virtually their exact color spectrum, so even if it was not the original intention, CMH goes hand in hand with indoor growing.
If for whatever reason I couldn't use my LEDs, and I had to choose a HID setup, it would be CMH. I've even thought of supplementing with them, but I'm out of room on my electrical panels at this point lol. My circuits are so overloaded, in fact, I might not even be able to charge this pho....
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