How To Compare Grow Lights

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Dr Photon
Member Moderator
Expert Grower
Completed Grows

Im going to try to be gentle. Haha. 😉

The flux values i talk about with integrating spheres are not the same as the semi flux measurements such as those from migro. As such they cannot be used together in the same conversation or comparison and are also subject to error. Fortunately migro has enough standards for me to accept them for comparison use of "his" measurements only (let me be clear on this, you cannot compare semi flux measurements from other sources. There are far too many variables for any kind of accuracy). Which is why they are the main values used in our LED product recommendations as it allows us to quantify differences between products.

Now. Some of the values you have mentioned are incorrect and need some addressing. CMH whether we use true full flux meaurements or semi flux values from migro, has been shown to be the same. With full flux its 1.5umol. Which has sub minimal error. Its the highest form of measurement with literally hundreds of thousands worth of equipment. Including state of the art spectroradiometers with minimal loss high efficiency integrating spheres. Which have to be big enough to house these massive fixtures in order to reflect light to a collection sump where the sensor lies. And by the way requires some extensive qualifications in physics and mathematics to understand how to precisely configure and tune the system to validate a correct measurement. Some insane level of complexity that i dont even pretend to know. But its much much beyond that of just a typical silicon sensor reading on the floor of a grow tent.

With migros measurements, the 315CMH has a semi flux value of 1.3umol, which is exactly the same as the 600w HPS hes measured. So theres two individual measurement data showing the same result. The 630 dual CMH fixtures cannot have an efficiency higher than a single fixture. They are the same system just with two bulbs integrated into the same housing. Its made that way because the target efficiency is designed around that specific 315 watts. And so in order to reach higher flux levels from the same fixture, they must be chained in parallel. But because of the added complexity on the reflector housing, additional heat and the added ballast load. This ultimately lowers the efficiency when doing so. As for DE CMH fixtures. It just simply makes no difference. Infact more often than not, it makes things worse. Double ended systems only works to improve efficiency with sodium discharge bulbs at a specific wattage. Working to shorten the arc tube and maximize the optimal temperature needed to reach its effective efficiency values for that "wattage". This is not the same principle with other bulb technologies, so there are no benefits, only drawbacks.

I can respect peoples experience but i am a man of science and i know to look at the data as a whole. And i know that no equivalent wattage CMH system has yeilded more than that of a sodium discharge system. The tests shows this and the science of photobiology explains no reason it should. I personally closed this topic for myself long ago so wont be going any further on the topic. 🙂

If you need any further convincing, there are several papers by bruce bugbee explaining everything here. Where he extensively does these meaurements and research on light technology for the horticulture industry. He leads the way and is unparalleled for todays progression in photobiology and lighting science.




Being wrong, is an opportunity for getting things right.
Posted : 11/27/2019 5:19 am Chefomj and Dr Coco liked

@drphoton, I’ve been trying to avoid nube questions but my research is all over the place.  I ordered a 48x24x60 tent.  I checked out your product reviews and felt the MARS HYDRO TSL 2000W Would be perfect.  Then I saw your review forCrecer Lighting PanthrX. I initially wanted to grow 3 plants but all reviews point to the latter. 

my question is this, on your reviews, you say expected yields per light.  Is that per plant per light or total or what?  Sorry again for the silly @$$ question. I checked the forum and did not see other asking (unless i missed it). Thanks and happy holidays to all!


Posted : 12/26/2019 6:28 am
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Trusted Member
Practicing Grower

Curious your thoughts/input @drphoton. 8 plant grow. I can run 4-600watt hids with 2 plants under each. Or 2-1ks with 4 plants under each. My simple mind only has with the 600s each plant would technically get 300watts per plant and the 4s would only get 250. But I know it’s more than that. Any input for me? Or advise?  I’d be able to add side lighting to the 1ks with adding my 600s but they’d only really hit the sides of the plants and part of tops.

Posted : 03/18/2020 7:04 pm
New Member
New Grower

Hi @drphoton hope you well,

So I am changing my grow lights,

I see these Led stuff its really confusing and more, on low budget

so I got to this company MEIJIU well rated it seems:

I still dont have a tent, kind of a storage with controlled climate

my setup are 6 plants  ( : : : ) I am thinking in one QB led for each 2 plants so 3 QB kits

I will give each 2 plants  2.62 x 2.62 ft

But they have a lot of QB and it is confuse cause they have same models diferent prices
Really dont know what to search:

Cant figure this out and the various options of colours (k) on these kits

@drphoton I really appreciate a educated guess


Posted : 03/29/2020 8:46 am
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