The Cannabis industry is thriving in all areas and, with so many new companies on the horizon, knowing which product is better and why can be hard work, especially when it comes to the technical world of horticultural lighting. To better break down all of the questions most of us have in the back of our minds, Humboldt sat down with Martin Anker from SANlight LED to get to the bottom of indoor lighting and to learn what really matters when it comes to what plants need.
By Stoney Tark
Hello Martin, can you tell us more about how you became involved with growing Cannabis?
Hi, Humboldt! 20 years ago, I started my first experimental indoor grow. Soon after, I developed a big passion for this hobby. Today the same passion drives me to develop outstanding LED grow lights.
Please explain how plants see light in comparison to the human eye?
Plants are using the same wavelength as visible light for humans. The big difference is the sensibility for different wavelength (colors). While humans recognize green light as very bright, plants are doing it conflictive. Plants absorb red and blue light best, and green light least. That does not mean that green light is not used for photosynthesis by plants, it only means that it is not as effective as red and blue light.
When growing Cannabis, what measurement of lighting output should a new grower be looking for?
Most important measurements are PPF and PPFD. PPF describes the total light output from a certain light source, while PPFD (Photon Flux Density) describes how many photons are "raining" to the canopy. More photons more yield. For flowering indoors, you should look for PPFD values bigger than 500μmol/(m2s).
So how are PPF and PPFD tested, and what do they mean?
PPF (photosynthetic active photon flux) can be measured in an integrating sphere or in a so-called goniometer. This measurement describes the photon count from all wavelengths between 400nm (blue) to 700nm (red), which is emitted by a light source. PPF is not weighted by a sensitivity curve. In comparison, lumens are weighed by the sensitivity curve from the human eye. This means for PPF and PPFD a red photon is counted in the same manner as e.g. a green one. The PPF value makes the comparison of different light sources easy, but it's not describing the full performance from the measured light source. To see the real world performance, a grower has to know the PPFD (photosynthetic active photon flux density) values over his complete growing area. Theoretically, the PPFD can be derived by dividing the PPF by the growing area. Practically the performance of lamps lights guiding system (optics, reflector etc.) influences the PPFD dramatically, especially in small rooms like grow tents. SANlight uses sophisticated secondary optics, which are generating a homogeneous light distribution with minimal losses to e.g. sidewalls from a grow tent.
Is there any bandwidth of spectrum the plants do not use when growing?
No, plants are using more or less all wavelength from 280nm to 750nm. The big difference is that wavelength from 400nm to 700nm is mostly used to drive photosynthesis. Another wavelength is mainly used to detect plants' environment. For sure this wavelength influences the morphogenesis and drug content.
What is the difference between white COB light and the red, blue, and green from LED?
COBs are based only on blue LEDs. Many blue LED chips are bonded to a silver-plated substrate which is coated by a silicone layer. The silicone potting is mixed with phosphor materials. The phosphors convert the blue photons to white light. As blue LEDs have a higher voltage drop and the color conversion is lossy COBs can't be as efficient as e.g. a red LED in terms of PPF efficacy. Red, blue, and green LEDs are so-called 'direct converted LEDs'. This means that the material combination from the LED chip itself defines the wavelength (color) output. Especially red LEDs with 660nm are very efficient.
Do you think UV will become more popular amongst indoor growers?
Studies have shown that UV light can influence THC content in a positive way. The problem is that the LED technology for generating UV light has a lack of efficacy. Additional good UV LEDs are very expensive and not long lasting. Tests have shown that the light spectrum in our products pushes THC content levels up to 25% THC when grown side-by-side with a leading HPS set up. Without usage of UV LEDs. Maybe, in a few years when technology is ready, we will start using UV LEDs, but not for now.
How important is red lighting and can you better explain how plants use red light?
As the photon energy of a red photon fits perfectly to the mechanism of photosynthesis, we can state that red light makes photosynthesis most efficient. All other photons, e.g. the blue ones, have higher photon energy. Following the plant has to transform the energy level to a lower level. This process is lossy again. The only problem is that plants can't use infinite amounts of red photons because of saturation effects from chlorophyll. As we are using high light intensities to grow cannabis indoors, we need broad-banded light spectrums to prevent bleaching and saturation effects.
Are LEDs superior to HID lighting in your opinion? And, if so, how?
Definitely. Today LED technology is much better than HPS technology. Single-ended HPS lamps are producing around 1.3μmol/J, while good LED lamps are able to generate up to 2.7μmol/J with a much broader spectrum as an HPS bulb. Double-ended HPS technology is producing their light output with around 1.8μmol/J system-efficacy. This means the energy savings are from 33% to 50%.
Additional LED technology can produce better and more sophisticated light spectrums which are influencing crop quality. In sum, a grower can produce the same yield with better quality by saving up to 50% energy costs. Especially at bigger projects the lower amount of heat produced by LED helps to save costs for air conditioning as well.
What tips do you have for anyone who is thinking to invest in LEDs?
Don't buy cheap LED grow lights. Most cheap lights are not performing or are not long-lasting. Have a look at datasheets or PPFD plots. Also, have in mind that the radiation angle of your LED has to be wide or use a multi-light source system. A lot of LED systems on the market have very narrow radiation angles, which makes them unusable in rooms lower than 3m.
Finally Martin... Where can people find out more about SANlight and follow you on social media?
Join us on Instagram or Facebook under "SANlight LED grow lights" or visit our webpage: www.sanlight.com. Thank you for your time, Humboldt!