Firefly Growlight

Full Spectrum Sunlight

Full Spectrum Sunlight

Ever since the beginning of mankind, light has been at the center of our existence. Imagine the darkness of the world before we were able to harness fire in the night. We have come far since then with artificial light sources that boost plant and even people productivity. In this article, we will add to your knowledge of growlights, by summarizing ongoing research topics as well as introducing our own ideas about growlight.


Since the 50’s of the 20th century, developments have been directed towards mixtures of various gases and finding their optimum flash temperature to emit light. High Pressure Sodium-bulbs (HPS) and Metal Halide-bulbs (MH) being the latest in this string of technology. These light-sources needed a high power-surge to ignite the gases inside the bulbs and after that a relatively high energy consumption to remain the state inside the glass. Besides the high light output, these lights are well known for their high heat-output as well.

The beginning of the 90’s saw the first Light Emitting Diodes (LED), weak reds, that emitted almost pure light and hardly any heat. Even though these initial units could not be used to grow a plant because of the low light output, the efficiency was clear. Especially when white and blue diodes were added to the possibilities, the development of the technology was kick-started.

Fast forward to the 10’s of the 21st century, we are seeing the fruits of the developments. High power LED-fixtures that can grow plants autonomously (as opposed to just as support-light) and reach astronomical efficiencies in terms of power-usage vs output. The choice growers face nowadays is: do you want more light or same light and less power consumption?

We at Firefly like to give you a third option: “how about both?”

Full Sunlight Spectrum

The spectrum of the sun consists of PAR and more. PAR is just the part that we humans can see with our own eyes, ranging from Blue – Yellow – Red, between 400-700nm. The sun emits anything between 100nm-1mm which is partly filtered by our outer atmospheric layers, but a lot hits our earth’s surface. Plants do pickup more than our eyes can see; they are also influenced by UV (200-400nm) as well as Infrared (780nm+).

The angle of the sun respective our planet determines the color spectrum that actually hits the earth’s surface. In the morning and evening, there is more red and yellow (golden hour in photography) filtering through, whereas in the middle of the day there is more blue. In spring and summer, notice that the days are becoming longer, so relatively more blue comes through compared to dusk and dawn in terms of time. After the midsummer night, the days will become shorter as red and yellow begin to increase relative to blue again. However, blue will still be the dominant color for a few months into autumn. Furthermore, the closer to the equator one finds oneself, the shorter dusk and dawn actually last, hence more blue. Think about where your plants are originally from to maximize the efficiency of your growlight.

Originally, spring and summer are our main growing seasons where plants are sown, trees and shrubs build their foliage and start preparing fruit development. During these seasons, midday has the strongest sunpower with the sun focused almost directly downwards. This happens to be the spectrum on which we at Firefly have designed our LED-growlight.


To rate the quality of your growlight there are a whole bunch of criteria which are flung around casually, however what do they mean and which ones are worth looking at?

How to rate the quality of your growlight


The actual power consumption of your ballast and light combination. This is usually calculated/estimated so it could be worth it to measure it yourself to see how accurate the numbers are.

PPFD. Photosynthetic Photon Flux Density

It counts the number of photons within the PAR-spectrum that are blasted on a set surface per second. It is the most common qualitative measure nowadays which can be measured and compared quite objectively by comparing PPFD surface charts that are made with the same distance between the light and the surface and the same surface-size in m2. However why only measure the PAR-spectrum when there are shown benefits of lightwaves outside this spectrum? PPFD is measured in μmol/s/m2.

PPF. Photosynthetic Photon Flux

Take away the surface from PPFD and you should get PPF. This measure is used in many marketing-rooms to calculate another popular measure of efficiency: μmol/J. By dividing PPF by the wattage of your growlight, you get this number and it basically says how much of the power used is transferred to PAR-photons. The problem is that measuring the total Photon output is not so straightforward as it seems. The best way is to use a spectrometer that is integrated in a sphere, which is easy with an HID-bulb. However how do you measure this objectively with a 1.2m2 LED-lilght-fixture? The answer is: you can’t. So when LED-manufacturers mention some kind of umol/J efficiency on their fixtures, bear in mind that they all use different ways to measure/calculate/hypothesize and they have a strong incentive to inflate the specs;

PFD. Photon Flux Density

Measure of all photons emitted on a set surface. This measure includes the UV-A and Far-reds that also benefit plant growth. Firefly LED’s emit light ranging from 350 to 780nm; and plenty of it;


Measure of light-color “warmth”. The higher the number, the more white the light. However, nobody uses this measure as a qualitative criteria about their growlight;


If a salesman of growlights starts talking about Lumen, just walk away…

What is UV-Light

The lower bandwidth of the light spectrum is called UV-light. It is invisible to the human eye, but it has a powerful effect, such as on our skins. We classify UV light in 3 groups: UV-A (315-400nm), UV-B (280-315nm) and UV-C (100-280nm). Lower then 100nm falls in the category of Röntgen or X-rays. UV-B and UV-C don’t have much use for plants and long exposure is dangerous for humans. The benefit for plants is in UV-A, and more particularly around the 350nm mark. It has proven to help keep plants compact as well as increase the production of metabolites. Metabolites can be terpenes, but also amino-acids and cannabinoids such as CBD, CBN and THC.

What is Green light

Most growers focus on the quantity of Blue and Red in the spectrum. This makes a lot of sense, because these colors get the quickest results in terms of chlorophyll production and thus plant response. In the times when LED-growlights were not so far developed as they are now, the focus would have been on getting Blue and Red as high as possible to prove the efficiency with regards to traditional HPS/MH light-systems. However, the LED-development train has long passed this station and thus we can again speak about Green Light. It is still expensive to make and incorporate into LED-fixtures, so most producers will use white-light LED-chips that give some Green as well.

Green light, as opposed to Red and Blue, is not absorbed by the canopy the same as Red and Blue. It partly bounces back as well as penetrates the top-leaves to reach lower leaves. Furthermore, if leaves are saturated with Red and Blue photons, Green allows these leaves to absorb more light. Especially with high power PPFD lights, this can be a big added benefit. Thirdly, Green light will increase CO2 absorption in lower palisade cells, hereby indirectly boosting photosynthesis.

Red:Blue Ratio

The old ways of looking at what the plant needs, basically answered the question: “what can we produce with blue and red LED-chips?”.

There were all kinds of analysis of growlights vis-a-vis chlorophyll production inside leaves and the result was a graph that was similar to the chlorophyll production schedule. These papers were well-read, and more LED-producers started to create the perfect growlight that matched the perfect spectrum. However, for some reason, LED-growlights were still not outperforming their HPS/MH light-systems in terms of yield. In fact, even nowadays in terms of output, HPS and MH are good powerful alternatives to some expensive LED-fixtures. However, they run hot, use more power, have shorter life-expectancy, bulbs need to be changed etc. We at Firefly have been able to mimic the actual solar-spectrum, comparable to a summer’s day at noon. This means that our LED-fixture will output a ratio of Red:Blue of around 1.9.

What does Firefly offer?

We have designed a high-end fixture that uses only one LED-chip, but can still provide your plants with the right balance of colors as well as plenty of power to make any plant grow. The spectrum that we are giving, is the same spectrum that the sun gives on the highest point in the sky, during summer. If that doesn’t make your plants happy, nothing else will. This is a unique feature that no other competitor offers at this moment.

Our Firefly LED 600W fixture is completely modular, which makes it possible to modify the setup to optimize the light-spread to any grow-area. This has to do with the lenses that are placed close to the actual LED-chips that will spread the light beam in a 60o angle. For grow-areas up to 1.2m2 we advise to set the fixture up by attaching all 6 lightbars to create one fixture. If your plants are somewhat larger and reach within 80cm of the light, we advise to break up the fixture in 2 by splitting the unit in the middle. This 2x 3 lightbar setup will also work well in 1.5m2 grow surfaces.

Finally, our Firefly LED is up to standard with all modern growers’ demands; it is dimmable, controllable, IP66-waterproof and unlike some other units on the market: it is compact and very very sturdy. It has the highest impact rating available to luminaires: IK10. We accidentally dropped a unit down from the second floor and it was still working afterwards.

We invite you to have a look on our website to find out more about our Firefly LED fixture, HPS-fixture, Controllers as well find out more about our company, future projects and how we may be of service to you.