Many people are looking for a single metric to compare different grow lights. Some people think the larger the PAR, PPFD, Lumen, Lux or μmol/J the better. While these metrics are very important it does not provide full insight. First of all let's name these metrics:
PAR: Photosynthetic active radiation. This is basically the amount of that is light inbetween 400nm-700nm that is emitted by a light-source which is relevant for the plant's photosynthesis process. Note that it does not include far red and UVA.
PPFD: Photosynthetic photon flux density. This includes the amount of light that reaches the plant's leaf surface or any surface. It is light inbetween 400nm-700nm per m2 per second.
PFD: Photon flux density. This is the amount of light that reaches a surface and can be with any nanometer range. e.g. PFD-R is PFD in the red area which is 600nm-700nm.
μmol: Micromole. The unit of light that is relevant for the plant.
Lumen: The amount of light emitted by a light source that is relevant for human photopic vision.
Lux: The amount of light on a surface that is relevant for human vision.
A single metric can be optimized, e.g. you can have a high PFD while not providing the right PFD (read more below).
When comparing grow lights, there are important things to consider:
The intensity of the light: Plants require light for photosynthesis and other processes such as flowering time management. Installations that are too intense can cause tip-burn, inefficient nutrient intake and other growth abnormalities. Too little light is also bad as it can cause plants to elongate, grow slow and weak. Intensity is often expressed in umol or micromole. A good supplier will be able to provide you with the total output in umol, and also for the different spectrum ranges. For tissue culture fixtures output can go up to 75 umol, for vertical farming up to 300 umol and for greenhouses up to 3000 umol.
Spectrum: The photosynthesis process in plants is driven by light and light mainly in the 400-700nm range. This includes high energy light such as blue, green and red. For photomorphology light in the 700-800nm such as far red is important. A relatively large share of blue and red are often desirable for during general growth and development process. Far Red and UVA are often not required in large ratios.
Full spectrum could be relevant too. The natural light from the sun contains a wide range of colors. There is an increasing body of research that suggest that apart from blue and red, more colors are having a positive effect on plant growth and development. Please note that many lights claim to be full spectrum but they are essentially regular white leds which are great for human vision, but not efficient for plants. Full spectrum for plants should have higher peaks in the plant sensitive photoreceptor areas. A higher peaks in these areas makes the light more effective for plants.
Adaptability for your crop and future crops: Dimmability helps to optimize intensity for your current crop and future crops. For example when you grow young plants you use less light, when they become bigger they need more light. Even better is if you are able to adjust the individual ratio's of PFD so you can create completely different lighting recipe's and have the possibility to run algorithms too. Note that LEDs consume less energy when dimmed.
There are many other metrics that are relevant for people and you should explore if they are relevant for you as well. This includes metrics such as lumen, CCT, CRI and so forth. CCT is the color temperature of the light. CRI is the Color Rendering Index, and is an index to indicate how truthful you are able to see colors. For indoor vertical farming and increasingly in the greenhouse and tissue culture labs these metrics are added as they enable people to see the plants well and can help to avoid dry eyes. This is especially the case when the lights are purple.
The best way to compare any professional horticulture lights is to perform an A/B test with your regular set-up and a set-up with new horticulture lighting. Each tissue culture lab, vertical farm or greenhouse and grower has its own unique needs or attention-points. e.g. different growth media respond different with lighting and temperature has a relationship with lighting too.
HortiPower offers a trial period on any one of our lights to help you find the right lighting that works for you and your plants, flowers or tissue culture. Seeing something with your own eyes is better than us telling you.
If you have any questions, email us.