Expert Lighting Advice For Taking Your Grow To The Next Level

When you’re first starting out, certain details, like lights, can be intimidating and pose a challenge.
Expert Lighting Advice
Cannabis plants thrive under the right spectrum/ Courtesy of SANlight

Investing in the latest and greatest technology can help you take your grow to the next level. However, it can be difficult at times to know which lights are worth investing in. We speak to Martin Anker from SANlight to better understand what to look for in a grow light and how lighting can increase your yields.

How did you first get involved with horticultural lighting?

Almost 20 years ago I started as a hobby grower. I was growing on just a few square meters with HPS [high-pressure sodium] lights. As my grow setup had to be as stealthy as possible, I realized that temperatures in small cabinets are a big issue to control. A few years later I started mechatronic studies under a master’s program, where I decided to combine my hobby of growing with my technical knowledge, and eventually founded SANlight.

What’s most important when considering a grow lamp?

Many different points have to be considered, and the first question is where you want to use your grow-light system. For usage in big professional facilities or greenhouses, the protection of LEDs [light-emitting diodes] is important. So you need at least IP54 protection class. Especially if the grower is working with sulfur, the protection is very important, as sulfur can destroy your LEDs.

For sure, the PPF and PPFD [photosynthetic proton flux and photosynthetic proton flux density, respectively, which are measures of photons that contribute to photosynthesis] values are most important in general. A grower should have at least the same PPF and PPFD readings as with their old HPS system. A few percentage less PPFD can be compensated by the better spectrum, however over 15 percent less PPF/PPFD will lead to smaller crops. For example, a 600-watt HPS SE [single-ended] fixture has around 840μmol/s PPF, so your LED system should have the same or more PPF to be a good replacement.

Light spectrum is important also, and narrow-banded spectrums with just red and blue LEDs will lead to saturation effects on chlorophyll when used at high intensities greater than 500μmol/m2/s. Such PPFD values are typical for growing cannabis indoors. Last but not least, a grower has to check for passive-cooled fixtures and the lifetime of the whole fixture’s good secondary optics. As the LED technology is rapidly moving forward, a grower would benefit from an upgradeable fixture, saving the grower money in the long run.

What is the difference in the brightness of a lamp and the PAR output?

Brightness is measured in lumen and lux. On the other hand, the human eye can see green light best, which is the measurement of lumen—the sensitivity of the human eye. Due to the technology nowadays, most HPS bulbs have the same spectral output. Therefore, a grower can compare HPS bulbs by lumens even though it’s not the right measurement.

To evaluate light sources for horticultural applications, you have to know that you can look at light in two different ways. One perspective is to look at light as a wave—then we are talking about PAR watts. The other point of view is to look to light as particles [photons]—then the measure is μmol/s, which means we are counting the photons. If we are talking about PAR watts, you have to know that the energy of a light wave depends on the wavelength—the shorter the wavelength, the higher the energy from the light wave. Our internal research has shown that measuring photosynthetic active radiation is done most exact by measuring in photons [μmol/s for PPF and μmol/m2/s for PPFD].

Expert Lighting Advice
Anker’s lighting technology works for a variety of plants/ Courtesy of SANlight

Which spectrums of light do plants really use during their life cycle?

That’s not an easy question to answer, as the research for that is at an early stage. In general, my answer is the best spectrum for plants is emitted by the sun. It’s possible to design a sun-like spectrum with LEDs, but lifetime and efficacy are not good with today’s technology.

Whether or not a spectrum performs well or poorly should be the primary concern along with the intensity at the plant [PPFD]. For low intensities with 50μmol/m2/s to 200μmol/m2/s, narrowband spectrums with just red and blue work fine. Such intensities are used, for example, in greenhouses as a supplement to the natural daylight. If you want to grow short-day plants in an indoor facility, a grower needs high intensities, e.g., 500μmol/m2/s. For that application, a more broadband spectrum works better by preventing saturation effects. We are trailing different spectrums at different intensities continuously, and up to today our actual spectrum performs best for indoor cultivation at high PPFD readings.

How does red and far red influence flowering and why does this happen?

Having the right ratio of red and far-red light is important for rooting and the development of side branches. Without enough far-red light in the spectrum, side branches will stay very short, which leads to a reduction of yield at the end of your grow. Also, the root development of clones and seedlings is influenced by the red/far-red ratio.

Pure far-red light can be used to manipulate the maximum lighting time for flowering. Generally, short-day plants start flowering when the light cycle is 12/12. With additional far-red light at the end of the day, plants will start flowering even at 14 hours of light per day. So a grower has two hours per day more to power up the crop with light energy. But in my opinion, this is not the way to go, because it’s tricky to find the right amount of far-red light for different strains.

What are your thoughts on COB [chips on board] lighting and its overall efficacy?

COBs are good in terms of efficacy but are definitely not market-leading. It’s an easy way to build up DIY lamps. As COBs are silver-coated, they are not useful for professional horticulture lighting, because the silver coating will be destroyed by sulfur in a very short time period. The COB will still function, but the PPF will drop dramatically. In professional indoor farms, sulfur is used to prevent pests and fungal attack.

How exactly do lighting manufacturers test for PPF and PPFD readings, and how accurate will those readings be?

Measuring PPF can be done in an integrating sphere or in a goniometer. Once a manufacturer has this equipment in his facility, the measurements can be done easily. Of course, the measuring process itself has tolerances up to plus or minus 7 percent.

PPFD measurements are also easy to do if you have the right equipment. We have seen in the past that cheap PAR meters have measurement errors up to 30 percent; however, if you use the right equipment, the measurement can be done quickly. It’s important to measure over the whole area, and not just give a single value for a certain area, meaning it is best to have a PPFD plot over your growing area.

Do you think UV [ultraviolet] plays a role in the potency and terpene profile of plants?

Yes. With UV light, a grower can manipulate potency, but this is just one method of manipulation. Our standard indoor spectrum boosts the THC content more than 25 percent in comparison to a side-by-side HPS test. Without the use of UV, generating UV light with LEDs is not a good idea at the moment, as powerful UV LEDs are very expensive but not very efficient. UV light is also blocked by PMMA [acrylic] and PC [polycarbonate], which is the material for secondary optics.

Expert Lighting Advice
Cannabis plants get inspected in a massive garden lit by LEDs/ Courtesy of SANlight

Are LEDs more environmentally friendly, and can you describe the popularity of LED lights in Europe and how things have changed over the years?

Yes, on the one hand, the lifetime of LEDs is much longer than with HPS. This eliminates changing of the light source and, of course, reduces waste. Alternately, LEDs do not contain heavy metals like quicksilver. When I founded the company in 2012, it was hard to sell LEDs to the public. People doubted this technology, because a lot of cheap LED fixtures on the market produced bad yields in terms of quantity.

For SANlight, it was important to tell the people what’s possible with LEDs and what’s not possible. Today’s technology can save up to 40 percent energy while producing the same yields, with the quality of end product being better if you grow with LEDs. That means you have more THC and CBD in your harvest, and the terpene profile is better too, because of lower heat radiation. In German-speaking countries, growers have realized that. Home growers especially can benefit from using LEDs as lighting for their grows. Growing with LEDs means a grower can produce a larger yield in the same cultivation area.

How is the scene in Europe regarding CBD, as we saw you are involved with a large-scale project in Switzerland?

CBD production is a big industry in Switzerland, and many farms are equipped with SANlight LED fixtures. Using LEDs in professional growrooms reduces the need for air conditioning, makes it possible to grow cannabis in a vertical farm, and increases crop yield and quality. Many professionals believe that LED technology is a key factor to operating their farms more profitably.

Do you feel that more growers will turn to LEDs as laws start to become more relaxed around the world?

Yes, I believe in that. Also, as the LED technology has higher initial costs, people could be afraid to lose their lighting system if something goes wrong. As laws change in favor of legal growing, growers will not have to worry as much about their grows being in jeopardy and could be more willing to invest in the technology for the long haul.

What are your top tips for anyone who wants to get the most out of their grow light?

A couple things. In our research, we have seen the importance of VPD [vapor pressure deficit]. And, of course, checking for temperatures above 23°C in combination with the right humidity is a key factor for good results with LEDs. Feeding and any other factors that influence plant growth can stay the same as with HPS. The only thing that changes is the needed amount of nutrient solution per day.

Do you have any social-media platforms our readers can follow you on?

Yes, you can find us on Facebook and Instagram (@sanlight_led).

This feature was published in the July, 2019 issue of High Times magazine. Subscribe right here.

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