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When looking for the right lighting system for your growing operation, it is easy to get bogged down with tables full of numbers and acronyms. What numbers should you be looking for when trying to decide on the best grow lights for plants?
While all of these terms do relate to lighting, only a few offer meaningful insight into the quality of light that plants require to stay healthy, flourish through the whole growth cycle and to ultimately provide a great harvest.
What you need to know before making a decision
Don’t look for Lumens
The lumen is a measure of how bright a light appears to the human eye. There is no correlation between our vision and photosynthetic growing rates, so don’t bother with this metric when looking for a horticulture lighting system.
Don’t look for LUX
LUX measures the intensity of light using lumens/m2 typically for residential and commercial applications, like buildings, parking lots, etc. Since this metric is based on lumens, it is not an applicable way to evaluate lighting for plants.
Don’t look for Foot Candles
Foot Candles are similar to LUX measurements, but based on feet instead of meters. As with LUX, this metric is based on lumens. Important for the human eye, but not for plants.
Know the Watts
Watts refer to the consumption of electricity of a particular light. Watts can help you understand the cost of running your lighting systems, but that measurement alone doesn’t tell you anything about the system’s ability to deliver light to the plants.
Know the PAR
PAR stands for Photosynthetically Active Radiation and it represents the range in the electromagnetic spectrum where photosynthesis is most efficient (400 to 700 nanometers (nm)). This is the light your plants love!
PAR is not a unit of measurement (like feet, inches, or kilograms), so it is often misused in the description of lighting systems. PAR defines the spectrum of light and it is usually given as a percentage. About 50% of natural sunlight falls within PAR. Lamps that emit a high percentage of PAR light are more efficient, since more of it can be used by your plants.
Know the PBAR
PBAR stands for Photobiologically Active Radiation and it represents the spectral range that plants use to produce energy. It includes portions of the Ultraviolet (UV) and Infrared (IR) spectrums not visible to the human eye, but useful for plants.
Like PAR, a percentage of PBAR describes the amount of light emitted that falls within the range that plants can use.
Always check the PPF
PPF stands for Photosynthetic Photon Flux, and is measured as the number of micromoles per second (μmoles/s). PPF measures the quantity of PAR at a specific location every second.
Light is made of particles (photons) so think of a low PPF as a trickle of light hitting your plants, whereas a high PPF is more like a widespread rain storm.
Always check the PPFD
PPFD stands for Photosynthetic Photon Flux Density and is measured as μmoles/m2/s at some distance from the light source. PPFD measures the amount of PAR that actually arrives at the plant per second, in a specific area and at a specific distance from the light.
This is the best metric to use when comparing lights, because it tells you exactly how much of the right kind of light your plants will receive. A high PPFD rating represents dense light which is also evenly distributed across the canopy.
Sometimes lighting vendors will describe high PPFD measurements by measuring photons directly underneath the light instead of averaging an entire area at a reasonable distance from the light. Don’t forget to check the total area used to calculate the PPFD, as well as the distance from the lighting source.
Always check the Spectrum
While it is essential that your lighting system delivers the optimum photon light density (PPFD), the full spectrum of sunlight has the highest impact on the development, quality, and robustness of plants.
The sun’s spectrum is critical for two plant processes: photosynthesis and photobiological reactions that regulate plant growth and medical compounds.
How to choose the right lighting system
To install the most efficient lighting system to meet cultivation and business goals, the PPF, PPFD and Spectrum measurements are a must. Once you have those measurements at hand, it becomes much easier to compare lighting systems and choose the best grow lights for your plants.
If you have any questions about the metrics discussed in the article leaves us a comment below!
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How To Choose The Best Indoor Lights For Plants
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