Ceramic Metal Halide CMH 315W Lamp Comparison Test Data & Review

Download the Zoomable PDF HERE: CMH_COMPARISON1.pdf

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Hey everyone Nate with Growers House here and we just wrapped up our test on 315 watt Ceramic Metal Halide Lamps. Were trying to tease out which lamp available in the market is the best for growing plants. I scoured the market and got my hands on every single 315 watts ceramic metal halide lamp I could, with the intended use of growing plants of course.

We ended up with 10 bulbs and from those ten bulbs we put them through a battery of tests trying to keep all variables constant except for one. Our aim was to record the spectrum of these bulbs and get as much data as possible - data we can then pass on to you. Data to help you to make a decision on which lamp is going to be best for your grow, whether its the best output, the right spectrum or just the best value. That decision is totally yours,  we just want to provide you with all the information that you can use to make an educated decision. But first, a lot of people don't know about ceramic metal halide lighting, what it is or where it came from. First, just looking at this lamp you can see it's pretty small and has a different kind of socket than the usual Mogul style socket and requires a specially designed 315 Ceramic Metal Halide Reflector and or an CMH Bulb Adapter and enabled to be able to use them.

I want to first and foremost lets clarify one point - CMH is NOT a Metal Halide Lamp. Most people think Metal Halide Lamp, "I know what that is.. ok this lamp is made for veg."

No, that's not true. Lets take a look at a Metal Halide Lamp. A CMH lamp has a different emitter than a normal metal halide lamp, which is built of Quartz.  Inside a CMH there is a ceramic component. So the difference is this - A ceramic tube is able to withstand much higher temperatures. Many manufacturers are saying the higher arc tube temperatures happening inside the lamp allow for more color stability, better lumen per watt ratios and effectively an all around better bulb in comparison to the HPS metal halide. We're talking about how many photons of light you're getting to your plant in the usable spectrum per watt of input, which is really the way you want to measure efficiency for your lamps.

CMH lamps burn just like a normal Metal Halide Lamp. There are salts inside of the arc tube that heat up to a high temperature and that give off a certain spectrum. But, since the salts inside a CMH are able to heat up to much a high temperature they're actually turned into what resembles plasma. Plasma burning at this higher temperature has the effect of providing a spectrum that is much wider and better than traditional HPS or metal halide lamps.

So that's why these ceramic metal halide lamps are so popular these days because people are looking for the little edge in getting every efficiency of their garden possible and to be honest, Ceramic Metal Halide is kind of the new wave of the future in terms of getting there. So let's jump into some of these results that we have I want to show them to you because we got a little data crazy, doing some different spectral analysis some bar graphs and of course some light layout measurements and we also came up with essentially our own graph of what we think the best value is for your garden in terms of overall output and price.


Starting off looking at the spectrums of these two different lights, really there are two categories of ceramic metal halide lights. Approximately 3,000 Kelvin and approximately 4,000 Kelvin, with the 3000 Kelvin you can see that most of the intensity of the light is focused around about 600 nanometer range, that's where its strongest and you see that like really Orangish almost Yellowish Hue you see along with HPS light, so that's why it looks a little bit Orange to your eye and you also see when you get up more towards the IR there's a pretty big spike there just north of you know close to north of 800 nanometers and then it drops off and there's not too much past 900 nanometers.


Now if we look at the 4000 kelvin spectrum you'll notice that it actually looks a little bit more full that's because the spectrum is a little bit more broad but when you compare these two, what you can't really see is that the 3k is more intense, but the 4k has a little more of a broad spectrum. So that broad spectrum you see is a little bit closer to like the I would say its peak is closer to around that 500 range and that's why you see the light a little bit more as like a white light or even what people call blue light which more resembles even like your metal halide and usually out of the 4200 Kelvin lights you will see a little bit more going into the UV range although when we did some testing we did see that UV is were actually pretty high and some other 3k lights as well.


For this test our measurement of UV is relative- by measuring the intensity of the light between 250 and 400 nanometers and that range is primarily going to be focusing on the UVA and UVB these lights give off. The light that did best in terms of UV was the Ushio 3000 Kelvin CMH Lamp which was a little bit surprising and then the next up was the Nanolux MaxPar 4200 kelvin CMH Lamp. So working your way down you'll see that the difference between the lowest bulb and the highest bulb isn't significantly great I mean these are relatively low numbers if you're thinking of par so I wouldn't say that these lights are a very strong UV performer but they do provide some UV indeed but the range between six and eight point six for light of this size actually you know 315 watts is actually really not that bad, but if you’re looking for max UV I'd say go with that Ushio.


We made our PAR footprints to show how this light performed in a Sun System 315 Watt LEC Fixture on 120 Volt so keep in mind the inside of that fixture has some pebbled aluminum in it.


Our footprints which show a center readings for five sizes. 1x1, 2x2, 3x3, 4x4, 5x5  and the par readings at each one of those points. Keep in mind the pebbled aluminum aluminum can kind of shoot light in different directions it can scatter it a little bit. So really when you're looking at this don't take the Center reading as gospel, really the most important thing is to take as many measurements as possible and in this case when we take the measurements of each one of those parameters and add them all up and gives you a much more well-rounded story of how well this lights producing in the whole I mean when you're testing lights on a very very scientific level like with the best instrument instrumentation available using an integrated sphere and you're measuring basically every single, I mean we're talking multiple thousands points you're measuring with here we're doing you no more than 30 so you can see if you're looking at the center I mean the highest reading that we all have any light here was the Phillips 3100 Kelvin CMH Agro Lamp and it was pretty consistently the best across most of the readings. Taking that into account you know take a look at this noting which fixture it's in so that's the kind of spread you're going to get but of course when we do our testing we try to hold every variable constant except for one and that's what we’re testing for which in this case would be the bulb. So we used the same balance same height same reflector in the same ten you know everything was held to a standard where we feel like it was getting a to the point where pretty scientific.


Our part charts graphs includes the sum of the perimeters of each one of the 1x1, 2x2, 3x3 and 4x4 but the one that I want everyone to pay attention to most is the sum of all par for the 5x5 print because that's the one that takes the largest sample size of measurements into account. From the results of the 5x5 you can see that the Philips MasterColor 3100 Kelvin CMH Lamp was looks like by far probably the best overall CMH bulb available. It had the highest reading of all the measurements for PAR and when you look at the 4200 Kelvin version of the Philips CDM Elite 315W bulb did the best as well you know I mean going into this if I had to have a hypothesis I would say that Philips Elite 315W Brand would be my guess for the best bulb. Probably because Philips is company that designed and developed the 315 CMH lamp originally, perfected what kind of ballast to use with it, how it would work properly and their compatibility of the two both in Hertz and the wave type of the ballast so I would say kind of no surprise there.

Although it is a little bit surprising that Philips Ceramic MH Lamps did approximately eight percent more than the next best bulb which would be the SunPulse CMH 3200 kelvin bulb. The differential between the Philips CDM Elite 315W bulb @ 4200K and the next best 4200 k lamp looks like the Nanolux Max Par 4200K CMH Lamp is just under five percent.

We hope you can take these readings use them to make an informed decision on purchasing the best 315W light for your purposes you know 315 watt ballast and are relatively similar so which one you go with won't probably have a huge differential but it looks like these bulbs you can tease out that there are some differences so use the one that other was the most you be or the most intensity or the best spectrum with this information and if you have any questions for us please give us a call or send us an email and other than that, this is Nate from Growers House. Happy growing.

Download the Zoomable PDF HERE: CMH_COMPARISON1.pdf

4 thoughts on “Ceramic Metal Halide CMH 315W Lamp Comparison Test Data & Review”

  • William Felix

    Can you tell me what height was the light in making of the PAR footprints?

    Thank you

  • Rod Wilt

    Very informative 315w light study. It has been difficult deciding how to upgrade my lighting situation, until I spoke with a couple of c/s rep's. Both were very professional and knowledgeable on all their light products that would best fit my needs working within my budget. It's always a pleasure doing business with The Growers House Store. Thank you, your loyal patron, Hydrorod

  • Adam Saadeh

    EYE Hortilux advertises that they use a special type of glass in their CMH bulb that doesn't block UV spectrum, when you look at it closely you can see it looks quite differently than other CMH bulbs on the market, first it is much "fatter" and a bit longer than other CMH bulb which seem to be quite standard across the board, though they do fit in a normal CMH fixture. I'd be very interested in exactly how much UV is being produced and able to reach the canopy. I have a LUX meter and my canopy at the same height seems to be getting quite a bit more light. Id love it if you guys can do a thorough review and update this post or create a new one.

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