I once heard that connoisseurs grow with MH bulbs and commercial growers used HPS. Is there any truth to this?
What
@RM3 said, and I'll elaborate; HPS was always good for producing lots of the red spectrum plants need to grow and get big, but they lack the blue spectrum for good resin production.
MH was historically better for resin production, at the cost of yield relative to using HPS.
Newer lighting technologies have rendered both of these technologies obsolete, both in terms of PAR/Watt performance and spectrum.
RM3 has chosen the approach of lots of 4' T5 lamps over a relatively small space, which suits his quantity needs and allows him to play with spectrum options, as there are a wide variety of 4' T5 lamps out there now. While it's arguably not as scalable an approach as more high power lighting, the level of control over spectrum is unmatched, certainly at anything approaching a regular guy's budget.
COB LED is another form of lighting that's set to take over because of efficiency, scalability and superior spectrum. The only thing they lack is UV output, but I think this is a blessing in disguise; this way, a grow can install a circuit with nothing but UV sources and thereby control it independently in order to get desired responses- and importantly, be able to shut them off when people are working to prevent exposure. My own limited experience with COB LED (but growing every day!) leads me to the conclusion that they're not just easier to work with and grow under, but the broad spectrum plus peaks in the right places makes growing high quality product an 'easy mode' proposition. And that's without any UV supplementation.
Plasma lighting is being tried, but I think it's a dead end tech; too expensive and finicky compared to COB LED, and less flexible.
New tech is coming out all the time, and newer forms of LED lighting now on the horizon just might improve on COB LED performance.
One thing is for certain; LED of all types will continue to get even more efficient, even better spectrum and ever less expensive. Period. That simply cannot be said for HID technology.
If you're not ready for LED, I'd recommend the 315W CMH system, or its bigger analog, the 860W CDM Allstart. The key to best performance from these next generation MH style (now with a solid ceramic core) is the ballast; they MUST be operated with LFSW, or Low Frequency Square Wave ballast technology. This is easy with 315W CMH systems, as 'most' already use them. Make certain whatever system you get has it.
As for the 860W Allstart, I'll be taking delivery of one of
@Revolution Micro's new integrated fixtures, featuring both DE mounting and LFSW technology. My first goal with it is to see how it drives the 860W Allstart. (ignore the 860W number; it was a rather thin marketing promise based on running the bulbs with magnetic ballasts on 208V service, they run the same 1000W as everything else at 120V, 240V, 277V, etc). Early testing has indicated that as long as the ballast is an LFSW type and compliant with the lamp's requirements, in this case frequencies below 174Hz, it should work.