What You Should Know About: HID - Ceramic Metal Halide

Available at nearly any respectable hydroponics shop, you can discover the innovation of ceramic metal halide grow bulbs. This type of high-intensity discharge (HID) light has been specifically engineered to resemble the spectrum of light put out by the sun, closer than any other grow light out here. Best of all, is the fact that one CMH light is perfectly suited for both vegetative and flowering cycles.
Additionally, you won’t need an expensive digital ballast with these lights, but rather a standard ballast for HID lighting. Using a digital ballast can actually harm CMH lights.
Depending on the brand you choose, 400watt ceramic metal halide bulbs will put out anywhere from 32,000 to 36,000 lumens, have a bulb life around 15,000 hours, and can typically be places horizontally or vertically. CMH lights also make plants grow slightly faster than normal. If this is an unwanted trait, simply add some silica to the soil, which should slow this process down to a normal level.
CMH bulbs can also get quite expensive, but are worth the cost and will save you money in the long run. Just think about the fact that now you only need one bulb for all your needs.


Doesn’t the suns spectrum change over the course of the year? I thought that was the purpose of changing to an HPS

I don’t use HID but why does everyone change bulbs if the better method (not switching bulbs) is the easier method?

Not discrediting the effectiveness of cmh, but leds are available in just about the same cri.

That number also relatively easily achieved and exceeded by leds on a lumen per watt basis. And they can have life expectancy of around 50,000 hours with usually about 20% reduction in output over that time.

The big difference there is that lec will come in quite a bit cheaper than leds that perform at that level. The lec is a pretty solid choice when it comes to horticulture lighting, but it’s definitely not the only option at those specs.


Is it just me, or does this sound like an ad?

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Traditional HID’s were either red or blue in spectrum and don’t tend to hit full spectrum
CMH bulbs are more even in both red and blue as well as UV and IR and have higher PAR/W than mh/hps lumens are a measure of visible light what we see is less important than what a plant can use. Full spectrum LEDs work by using mostly just reds and blues making blurple a LEC produces white light while providing both red and blue at less heat than it’s HID kin thanks to double jacketed bulbs. HPS uses a ceramic rod MH uses metal halide gas in glass tube, a CMH uses Metal halide gas in a ceramic tube there by blending both lights into one :wink:
Where they differ most is in CRI color rendering index sunlight being 100 CMH are 90+ with MH/HPS ranking 60-70 range LED’s rank from 70-80’s. This means plants are always true color flower and veg

Actually depending on bulb at 15,000 hrs you have lost 10-15% of lumen intensity a MH bulb will lose 20% after 8,000hrs as will HPS
@TDubWilly many actually use MH entire grow but it limits stretch in flower and doesn’t get through canopy the same making super dense top kolas but giving little energy to anything not directly in it’s light fine for scrogs but plants prefer both spectrums


lmao it does but point is to highlight it’s benefits

Plants under HPS 1000w

Plants under MH 1000w

under LEC 315

Need I say more?


I don’t disagree, was just quoting what my response was to. I thought those numbers were a smidge low personally. Pretty sure I’ve seen at least new bulbs test around 140 lumens per watt.

We have the ability of covering 400-700nm and beyond with white leds though. People are still making them and buying them as you stated, but not this guy. Here is typical high cri white led spectrum.


@Daddy you have a pic for comparison?

It’s that 3000-3100k range that gives the high CRI and people stuck on the 2700k flower 6500k veg thinking
High Lumen Output: Initial Lumens: 37,000. 120 Lm/W, 570 μmol/s, Color Temperature: 3100K
High Lumen Maintenance: 90% at 8,000 hours; 85% at 20,000 hours
Richest Spectrum Flowering bulb in market with a CRI (Color Rendering Index) of 90: A proprietary phosphorous coating on the outside of the arc tube provides the richest spectrum and produces more Photosynthetic
cheaper CMH bulb

Incredibly high 1.95 PPF (photosynthetic photon flux) per watt per second light source
3100k Color Temperature, High 92 CRI, 33,000 Initial Lumens (105Lm/W)
High 90% lumen maintenance at 8,000 hr / High 85% PPF maintenance at 20,000 hr

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Metal halide looks good!

1000w it should accept it uses 1000w :wink: also pretty sure that MH was my Hortilux dual spectrum? $180 bulb which was good for 9 months and toast by 1 year


Out of likes, but we actually have quite a few tools at our disposal in diy. Buying pre built, you pretty much have to go to timber rapid or maybe a few others. But I can get 3000k in 70, 80, 90, 95, and 97 cri. Same goes for 2700k, 3500k, and i think 4000k. When you get into the neighborhood of 5000k and above the reds aren’t there to match up.

Like I posted earlier, you certainly aren’t doing it cheaply. Or as cost effective up front as with a 315. I’ve posted this graph before, but it clearly shows the shift in 3000k 80cri to a 3000k 90cri.

Going to 95 or 97 cri not as noticeable change, usually a little more blue and a little less green.


So how accurate is this chart @Donaldj

I believe that should be umol per joule correct? Or what we measure par efficacy as. And the 570 umols per second is the ppf of the 315?

For reference a de gavita is like 1.7 umol per joule. It’s more light, but less efficient.

Getting off on tangents. I think they’re great lights, and a good value. They will probably crush the average led panel available on Amazon for sure.

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I think if you change the one bar from about 315nm to 350nm, and the other from about 360nm to 440nm it’s pretty damn accurate.

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What I can say for sure is my plants stay lush green until almost very end of flower and can get serious fall colors :wink:
I have said before would love to go full LED grow but only if going top end and equal watts I run 4 spaces at no more than 1000w total at any given time including fans/exhaust :wink: Flip Flop flower spaces 2 veg space and mother space

And yes have looked at some stuff from rapid led and HLG but would be $$$ to change and shipping and taxes plus US to CDN dollar factors hugely

For sure. Would be different story moving from hps to a top of line led rig. Being the led guy I am, there’s not enough performance difference to justify the large investment from lec. Plus you have the heating issue to deal with. You can get into the 2.2-2.4 umol per joule efficacy with cree top bins, vero 29 b’s, luminous cxm 22, or a couple of the bigger cities. Whatever you save there will end up going towards heat I’m sure.

300w 90cri is about $600 US $780 CDN before tax $93 duty around $120 $990 and I haven’t added shipping yet lmao just to give you an idea :wink: rapid led went to cart was 630 with 80cri and yes US again and bft


Just want you guys to know that I’m enjoying this conversation and learning a lot - I just wish it was in English.