#1. What Does Full Spectrum Mean?
All LED lights are composed of a bunch of diodes that are programmed to emit light at specific wavelengths. When a light claims to be full spectrum, it’s saying that it emits light at all the wavelengths of the visible spectrum, from violet to red.
All grow lights want to emulate the sun as close as they can, because all plants evolved to grow in sunlight. As the seasons change, the natural lighting changes slightly based on the angle that sunlight hits the earth. LEDs with full spectrum capabilities mimic this with an ability to adjust the ratio of colors being emitted from the light in order to produce photomorphogenic responses in the plants. Through the manipulation of the full spectrum of light, you can signal plants to grow taller, shorter, heartier, to flower sooner or later, or to maintain its current size.
Some LED lights do not offer full spectrum, and instead are loaded with mostly red or blue diodes. As red diodes take less energy to maintain, it will appear as though the light has a better efficiency rating, because it can produce the same amount of light for less power. However, because plants need the full spectrum of light, these red-loaded lights cannot fulfill the metabolic needs of the crop, resulting in smaller yields with less variety in terpene and cannabinoid profiles.
#2. Are LED Grow Lights Hot?
LED lights can heat up, yes, but nowhere near the same temperatures that HID lighting can produce. HID lights often necessitate the use of separately mounted cooling units that add cost and power usage. They also emit infrared radiation, which will heat anything it comes into contact with. To compensate, more air conditioning is needed, raising costs again.
LED lights can have either passive or active cooling, meaning they can keep themselves cool without external help through naturally occuring heat transfer, or will have a cooling unit built into the light. LED lights with superior passive cooling, like the Fohse A3i, only ever get as hot as a warm bath, and can be handled immediately after turning them off, with no need to wait for it to cool.
The A3i does this through the use of heat sinks, which add surface area to the compact light, and draw heat away from the source through conductive heat transfer. The heat is then able to be wicked away by the natural air flow in the room through convective heat transfer. All of this is done without using any electricity, so all the energy the light is using is specifically to make light, not fight heat, adding to the overall efficiency of the light.
#3. Why are LEDs more expensive?
LEDs have an initial cost that often seems more expensive than an HID system. However that cost is just for purchasing and installing the features. The cost for operation is actually dramatically lower than HID lighting systems. The energy efficiency of LED is the first and most obvious place that it saves users money. HIDs are not good at converting energy into light. A lot of energy is spent making infrared ration and heat, or used to power cooling units to fight the heat they generate. Light emitting diodes emit negligible infrared radiation. If kept cool, diodes work with greater efficiency, and if they’re passively cooled, that means no energy is being spent to keep them cool. So a grow light like the A3i, which is passively cooled, will take all the energy that it gets from the socket, and send it directly to the diodes to create more light for less work.
Because the efficiency of LEDs is so high, they can run for longer, and fade gradually, so they last for years without needing to replace parts. HIDs require bulbs, alongside a host of external additional equipment that not only need to be regularly cleaned, but also replaced. So it won’t just be parts that need to be purchased, but also labor!
Yields are also typically higher under high quality LEDs, so while bottom lines will lower, profits can still increase!
#4. Why do you use PAR instead of Lumens?
LED lights used for indoor personal lighting are measured in lumens, which describe our perception of ‘brightness’. Before LED, bulbs were measured in watts. A 1000W bulb would be brighter than a 60W bulb, because more electricity was running through its filament, which is what produced the light.
Photosynthetically Active Radiation, or PAR, is the part of the electromagnetic radiation spectrum that is useful to plants and algae to activate photosynthesis. Any instrument used to produce light for plants will be measured in how effectively it is able to produce light within this range. Therefore, any figures on a grow light’s effectiveness will be completely useless to someone who doesn’t understand what PAR is.
In PAR, different colors produce different effects within the plant. Blue photons inhibit cell growth, which may sound bad at first, but at low levels it can help the plant grow taller before it flowers. Green photons penetrate leaves, bringing light through the canopy to lower parts of the plant, and play a key factor in how our eyes are able to perceive plants. Red photons are great for photosynthesis, but lack the green photons’ penetrative ability. For plants, a combination of all three is necessary to achieve an optimal yield. Much like humans, a plant needs a diverse range of food to be healthy. Just one type of photon, and the plants suffer.
Lumens measure brightness and brightness only. It does not take into account how effective the light is at making plants produce photosynthesis, just how bright it is in your room.
#5. What is the best spectrum for growing plants?
This is a bit of a simplification, but the best spectrum for growing plants is the spectrum of natural light emitted from the sun. Outside of that heavenly floating orb, the closest thing we can get that delivers a similar spectrum is the full spectrum LED grow-light.
Because of the tilt of the planet and the angle at which sunlight hits it, the ratio of colors within the spectrum of light changes based on the season. Typically, higher end LED fixtures like the Fohse A3i will give you the ability to change spectrums that simulate seasons like spring, summer, and autumn. The Spring spectrum mimics the natural light levels of the season by supplying the plants with a higher concentration of white and blue light, and a smaller amount of red and far red light. This triggers a photomorphogenic response within the plant, encouraging it to vegetate and grow, as well as to start the flowering stage.
After the first 2-3 weeks in flower, switching to the Summer spectrum provides a higher concentration of intensity of red spectrum light, which tells the plant to not only continue flowering, but when mixed with far red, sends signals to the plant to grow even taller.
Increasing the amount of red spectrum during the first 2 weeks of flower will trigger the plant to stretch and increase internodal spacing. While growers can switch over to Autumn anywhere between weeks 5-6, the Summer spectrum can be used all the way until the end of harvest due to the natural light-hungry genetics of cannabis.
If you are wondering which seasonal lighting is best for cannabis, the answer is not so clear cut. Each seasonal spectrum is necessary to create a large and healthy crop. There is no catch-all setting you can leave a light at, because plants evolved under the sun, to grow and change with the seasons.
DISCOVER FOHSE’S POWERFUL SPECTRUM CONTROL AT ILLICIT GARDENS:
#6. How long will my LEDs last?
While LEDs last longer than HPS on average, how long that LED light lasts will depend on its efficiency. An efficient grow light will also have an extended life-time. While high pressure sodium and metal halide bulbs need to be changed out, LEDs will slowly dim over time, allowing them to be repurposed as their output very gradually dims.
The A3i from Fohse boasts some of the best photosynthetic photon efficacy figures of any LED grow light in the world. With the highest intensity on the market, and record shattering PPF figures, its dimming capabilities allow it to be run at a lower output, closer to where other lights max out. Since it’s not working as hard, the light is running more efficiently. This efficiency increases the lifetime of the fixture, providing decades of light from one fixture with no replacements.
To see what your light’s longevity is, check the L90 and L70 figures on their spec sheet. These show you how long it will take your light, running at full power, to reduce to 90% of its output, or 70% respectively. A light with 20,000 L90 will take 20,000 hours to lose 10% of its output running at full power. Keep in mind, lights running below 100% output will last longer than what’s listed on an L90. It’s just a helpful figure to guess at its prospective lifetime.
#7. Can I switch back and forth between LED and HID?
You cannot switch back and forth between LED and HID lights! Well, you could, but you shouldn’t. As the amount of light a plant gets changes, every other parameter in the plants environment needs to be altered. The amount of variables you would have to adjust to switch back and forth would be expensive and labor intensive.
Most grow rooms are built and configured around the conditions created by a specific grow light. In fact, lighting is the one piece of technology in the grow room that touches every other variable. Change that, and the effects ripple across the entire environment. This is what we call the Cascade Effect.
In Conclusion
LEDs tend to provide more light and less heat. When light is at higher intensity, plants will absorb more nutrients and water, consume more CO2, and go through photosynthesis at a faster rate. It’s the foot on the gas pedal of the whole plant growth process. With HIDs, there’s more heat, less light, and infrared radiation, which requires specific alterations in order to deal with these quirks. It’s best to just pick one light and adjust your environment to meet the specific needs of the plant under that light.
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