What is ceramic metal halide light?

First of all, what do you actually call these lamps? Ceramic Metal Halide CMH? Light Emitting Ceramic LEC? Or metal halide (Ceramic Discharge Metal Halide CDM)?
The truth is that all these different names speak of the same ceramic metal halide (CMH) technology. LEC is in fact a trademark of CMH. To avoid confusion, I will use CMH in this article, which is the most common term.
Ceramic Metal Halide lamps are basically a variation of MH bulbs with little HPS added to the mix. CMH uses a ceramic arc tube, similar to that used in the HPS bulb, instead of the quartz used in traditional metal halide lamps.
Ceramic arc tubes operate at higher pressures than quartz glass tubes, allowing manufacturers to make more accurate spectrum variations than previous technologies.

The advantages of CMH


There is a reason people are looking for CMH light and this is a huge list of advantages over almost any other light production option.
Balanced Spectrum
Not only do you get a more balanced spectrum that targets almost every sweet spot for your plants, but they are also better at turning electricity into usable light.
In comparison, HPS and MH use a lot of energy, producing light in ranges that are not used effectively by plants. This means that CMHs are more efficient in the PAR spectrum than HPSs or MHs, making them a better choice for a single lamp.

Color rendering index


They also have a more natural CRI (color rendering index). CRI describes how the color of a light source changes the way an object appears to human eyes, and how well subtle variations in color shades are revealed. The higher the CRI, the more realistic things are. CMH lamps are usually rated between 80 and 96 CRI, for comparison, the sun is rated at 100 CRI. This means that CMH bulbs will allow you to see the true color of your plants without making your room look yellow, blue or purple.

Ultraviolet radiation

CMH lamps provide UV (ultraviolet) radiation, which, although beyond the scope of our vision, is useful (at certain intervals and intensities) for plant growth and development. They produce UV-A, UV-B and UV-C light, but UV-C is usually very harmful to human eyes. So the highest quality manufacturers use a glass filter to block the UV-C output, leaving UV-A and UV-B output intact.
Note: All HID bulbs emit a certain amount of UV rays. The amount can vary and they are sometimes protected. But don't forget to watch or work around a light bulb with a broken outer glass jacket, because UV rays burn you, and this damage is cumulative.


Ceramic arc tubes are more durable, so they last much longer than MH and HPS bulbs. In fact, CMH lamps tend to last more than 24,000 hours, while retaining at least 80% of their original intensity in the 20,000-hour mark. This overshadows the general rule of replacing 10,000 hours for HPS and MH bulbs.
In summary:
• Balanced spectrum
• Better PAR efficiency than HPS and MH
• High CRI for visual appeal
• UV additives
• Lower heat output per watt
• Lasts longer than other HID lights


Disadvantages of CMH


Weaker in flowering than HPS


When it comes to flowering crops, HPS lamps are still "Kings". This is because HPS lamps produce more light in the red spectrum than CMH. However, the Danube is still going on. If you compare CMH with watt-watt HPS, CMH lights have a more balanced PAR spectrum than HPS lights. Research is still being done to see if the added benefits of better spectrum improve overall quality even with reduced yields. 
Heat power
CMH lamps usually produce a lot of light in the infrared part of the spectrum (above 700 nm), which causes them to emit a lot of heat. Although there is still less heat than other 400W HID bulbs, it is noticeable even if they consume lower power.


Initial price

Another disadvantage is the initial price. Usually high quality 400 W MH or HPS kits (including ballast, bulb and reflector) cost about BGN 300, and for comparison the initial investment for a complete set of 315W CMH is around BGN 700, which is quite a large initial investment. However, in the long run CMH will save you more energy.
In summary:
• Not the best choice for flowering
• High heat radiation
• High initial investment


CMH light spectrum

When it comes to general cultivation, CMH offers the most complete PAR spectrum in every HID bulb available on the market. There may be other, more focused lights, but if we go for the most fully balanced single growing light HID solution, CMH stands out ... and convincingly.

"EYE Hortilux Super HPS" Spectral Reading

If you remember that PAR is light in the range of 400 to 700 nanometers is the actual usable light from plants. You will notice that neither MH lamps nor HPS lamps offer a fuller PAR spectrum in one light. In general, MH bulbs usually emphasize blue and HPS red, which is why many manufacturers who want the perfect canopy combine the two technologies.
CMH can still be combined with HPS to further boost the red spectrum, which is beneficial for flowering.


Choice of ballast for ceramic metal halogen lamp

The specifics of CMH ballasts are a bit complicated. It is strongly recommended that you purchase a complete CMH kit instead of trying to retrofit the CMH lamp to your old ballast.
CMH usually does not work on most electronic ballasts due to the extremely high frequency of these ballasts. However, there are some high quality electronic ballasts that can perform CMH lights without any problems due to their microprocessors.
To avoid any problems and confusion, the manufacturers of CMH insist on buying a CMH kit that comes with the bulb, ballast and reflector, all connected together for easier use and installation.
The benefit of square wave ballasts needed to launch them is that you won't have to deal with the electromagnetic interference (EMI) problems that many manufacturers are testing digital ballasts with.


CMH vs. MH

First of all, ceramic metal halide and metal halide bulbs are not the same thing.
By comparison, the only downside I can think of for CMH over MH is the initial price. With that said, it is clear that CMH has a much better overall spectrum than MH, especially with this red boost in the 3100k and 4000k spectra. CMH also works cooler and produces much more PAR light when comparing watts to watts.
The most notable point is the time of degradation. Standard MH bulbs have a lifespan of about 10,000 hours. Which is less than 50% of the 24,000 hours for which CMH is estimated.
Even if they share the same technology, they have fundamental differences in the way they are constructed and how they work. You can't just use the new CMH bulb in the old MH ballast. Attempting to do so would be very dangerous.

MH points

• More affordable

CMH points

• Efficiency
• Significantly improved spectrum with a well-needed boost in reds above MH
• Prevents stretching
• Significantly longer life



As already mentioned, HPS lamps are still the king of flowering crops. And that's almost the only thing they have over CMH.
HPS lamps provide most of the PAR light as red light, which is exactly what flowering and fruit crops need at this stage of growth. But CMH lamps still provide a more balanced PAR spectrum that doesn't promote stretching, like red light from HPS, more PAR light per watt, and overall cooler performance.
My recommendation for anyone working with flowering crops is to use CMH as the main lighting and use HPS as a red light additive to promote the highest and highest yields. Another important point is that standard HPS must be replaced every 9,000 hours due to their significant deterioration over time.

HPS points

• Best available spectrum of flowering
• More affordable

CMH points

• Efficiency
• Balanced spectrum for the whole cycle
• Prevents stretching
• More than twice the usable life 


In this case, it all depends on what we compare. Garden LED lights have certain advantages over HID bulbs, as they are more energy efficient, produce very low heat and can be placed near the canopy without burning the plants.
But at the moment, LEDs are usually not recommended because they "perform worse" due to the fact that manufacturers incorrectly label their products with ridiculous claims. Although there are many upcoming LED manufacturers that provide factual descriptions of their products.
For example, there is SPYDR from FLUENCE, which outputs a more evenly distributed and focused PAR spectrum than CMH, while covering 1.2m by 1.2m with similar energy consumption. The downside is that this LED setup is very expensive. It costs about BGN 1,500, and at this price point the CMH setting is definitely a more affordable alternative, unless the conditions of low heat and proximity to the canopy are absolutely not necessary.
CMH against the LED battle is still going on, there are LED technologies like SMD and COBs that look very promising for domestic and outdoor manufacturers looking for cooler and more efficient lighting. Only time will tell who is on top.


LED points

• Can be easily targeted to specific PAR ranges
• Much lower heat production
• Much longer operating time 

CMH points

• Much more affordable
• Lower service life

What should you buy?

As a general rule, it is best to purchase a complete CMH system because of the problems you may encounter when trying to retrofit a CMH lamp with one of your old ballasts. If you have already decided that you want to grow with ceramic metal halide technology, then you have learned that they are slightly more expensive than standard HID options.