First, let’s clear up a point of confusion. I’m sure you’ve seen (even just in this article), several different terms and abbreviations. Ceramic Metal Halide (CMH), Light Emitting Ceramic (LEC) and Ceramic Discharge Metal Halide (CDM) all refer to the same thing. CMH grow light is the most common term.
Another point of confusion concerns their relationship to metal halide lights. CMH bulbs are a variation of MH bulbs, but they are quite different. Instead of using a quartz tube, they use a ceramic tube (more here), similar to an HPS bulb.
This allows a higher arc tube temperature, which in turn allows a better mix of gases to produce a more optimal spectrum. It is, for practical purposes, a perfect combination of MH and HPS in a single bulb.
Advantages of CMH grow lights
Broad spectrum
This is the first winning point of CMH over HID grow lights. CMH bulbs have much a wider and more consistent spectrum.
So besides having enough light intensity, plants also love to have sufficient light colors/quality to have their best growth potential.
More UV rays
Under high pressure, CMH bulbs can produce powerful light output that contains Ultraviolets (UV) like the sun.
These UVs include UV-A, UV-B, UV-C, especially UV-B which is really helpful for plant growth, overall all 3 types of UV are harmful to human eyes.
So you should not look at the bulbs directly for a long period. And most good CMH brands use a protective glass filter to block harmful UV types.
Long-Lasting
Ceramic arc tubes have an advantage over other tubes and bulbs because they are resistant to heat and other problems. This makes the grow lights last longer than others without breaking down. The grow lights run for 24,000 hours, which is equal to running for a period of three years. For 20,000 hours, the grow light keeps a constant lighting and heat strength of 80%.
Heat Consumption
Despite running at high temperatures, CMH grow lights produce less heat compared to many other grow light models in the market. The bulbs of the grow lights do not burn the leaves of the crops and it is one of the best options to use in a grow room or a GROW TENT for a good yield from efficient growth.
Efficiency
CMH bulbs give you a much higher PAR output (the amount of light that is usable by plants) per watt than any other type of lighting, apart from the most expensive LED grow lights.
Disadvantages of CMH
Higher Initial Cost
A ceramic metal halide grow light system costs, on average, twice as much as a comparable HPS/MH system. Of course, you will easily recover that cost within a year or two, since CMH bulbs don’t use as much power to generate the same output and don’t create as much heat either, resulting in lower cooling costs. You also won’t need to change bulbs as often. All of this is reversed when compared to LED.
Weaker in Flowering Than HPS
When it comes to flowering crops, HPS lights are still the “HID King.” This is because HPS grow lights output more light in the red spectrum than CMH lights. Even still, the debate rages on. If you compare CMH to HPS on a watt by watt basis, CMH lights do have a more balanced PAR spectrum than HPS lights. And research is still being done to figure out if the added benefit of a better spectrum improves the overall crop even with the diminished harvest.
Heat Output
CMH grow lights usually output a lot of light in the infrared part of the spectrum (over 700 nm) which makes them output quite a lot of heat. Although it still less heat than other 400w HID bulbs, it’s noticeable even if they’re consuming a lower wattage.
What do MH mean?
MH stands for Metal Halide. These are grow lights that give off a blue color and are designed to project a similar light to spring in order to aid the photosynthesis of your plants. For this reason, MH grow lights are specifically designed to be used during the vegetative stage of your plant’s growth cycle.
Why Use MH Grow Lights?
MH bulbs emit a cool white light (containing large amounts of blue).
MH lighting gets your plants to grow dense, lush canopies. It also prevents stretching during the flowering stage, which leads to a weaker branch structure.
Stretching can be caused by a lack of blue light, which is why MH bulbs are effective in preventing it. Growers flowering with HPS bulbs often see their plants stretch, since HPS bulbs emit virtually no blue spectrum light. Adding a few MH bulbs to balance out the HPS spectrum solves this problem.
Due to the lack of red wavelengths in their spectrum, MH lights are not good at flowering plants on their own, though.
Metal Halide vs. Ceramic Metal Halide
First of all, remember that although similar, CMH and MH are not the same. For comparison purposes, the only disadvantage I can think of CMH over MH is the initial cost.
With that said, we’ve made it clear that CMH has a much better overall spectrum than MH, with higher red and white light overall outputs. CMH grow lights also run cooler, and produce a lot more PAR light when compared watt per watt.
The most noticeable point is degradation time. Standard MH bulbs have a total lifetime of around 20,000 hours, but a quick degradation rate. Which is less than the 24,000 Hours that CMH are rated for.
MH Points
- More affordable
CMH Points
- Efficiency
- Significantly improved spectrum with a well needed boost in the reds over MH
- Significantly longer life time.
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