gradolabs
Hash me about LEDs.
This is a short article on photosynthetically active radiation, the bands of basically visible light that the plant uses for growth. I say basically because there is evidence the plant is affected by uvb and near infrared and IR light. All of this light is electromagnetic energy, whose carrier particle is the photon.
Photons are the quanta light travels in... that's what light is... just a bunch of these photons. Light has a wavelength. We measure this in nanometers. That's how small the wavelength is. Between 400 and 700 nanometers the entire visible spectrum can be described. Below 400 is ultraviolet light. It has lots of harmful energy as the smaller the wavelength is, the more energy the photon has. That's a rule of physics a guy named Max Planck figured out. German guy, born 1858, real brainy... so this isn't new knowledge. But now it's being applied to cannabis.
Above 700nm we start getting into IR light. Less harmful though it may disrupt flowering if it's too intense.
You can look at graphs detailing the absorption rates of photosynthetic pigments like chlorophyll a and b and for the most part they're all accurate even though they may differ on the exact ranges of usable light. None of that data is guaranteed accurate and to be frank you might not know the exact nature of the light you're using to grow.
This leads me to another point. PAR values are measured in micromoles per square meter per second. So imagine a photon is a ball... it's a 660nm red flowering ball and you have to put ten of those balls through a hole every second for maximum photosynthesis. Too many balls will bleach your plants and too few balls will revert to vegetative growth or something... it just won't flower.
Some of the steps I took to measure my PAR output was building a small spectrometer and taking a picture of the light output. Sometimes you can find data from the manufacturer but lab spec meters are very expensive.
When manufacturers state the PAR output though, I've never seen it organized in a uniform fashion. There's no ISO standard for horticulture PAR measurements that I know of because everyone's spectral output is different. I could have 1500 umol/m²/sec from 620-650nm red but none in 660 which is arguably necessary. Since there's no clear definition, your best bet is to learn as much as you can and make your own judgements. So be careful. Most lights out there have tried and true spectral outputs, but how effective are you delivering the entire spectrum required for your stage of growth?
Anyway, hope this helps. I can append more info if I forgot anything.
Photons are the quanta light travels in... that's what light is... just a bunch of these photons. Light has a wavelength. We measure this in nanometers. That's how small the wavelength is. Between 400 and 700 nanometers the entire visible spectrum can be described. Below 400 is ultraviolet light. It has lots of harmful energy as the smaller the wavelength is, the more energy the photon has. That's a rule of physics a guy named Max Planck figured out. German guy, born 1858, real brainy... so this isn't new knowledge. But now it's being applied to cannabis.
Above 700nm we start getting into IR light. Less harmful though it may disrupt flowering if it's too intense.
You can look at graphs detailing the absorption rates of photosynthetic pigments like chlorophyll a and b and for the most part they're all accurate even though they may differ on the exact ranges of usable light. None of that data is guaranteed accurate and to be frank you might not know the exact nature of the light you're using to grow.
This leads me to another point. PAR values are measured in micromoles per square meter per second. So imagine a photon is a ball... it's a 660nm red flowering ball and you have to put ten of those balls through a hole every second for maximum photosynthesis. Too many balls will bleach your plants and too few balls will revert to vegetative growth or something... it just won't flower.
Some of the steps I took to measure my PAR output was building a small spectrometer and taking a picture of the light output. Sometimes you can find data from the manufacturer but lab spec meters are very expensive.
When manufacturers state the PAR output though, I've never seen it organized in a uniform fashion. There's no ISO standard for horticulture PAR measurements that I know of because everyone's spectral output is different. I could have 1500 umol/m²/sec from 620-650nm red but none in 660 which is arguably necessary. Since there's no clear definition, your best bet is to learn as much as you can and make your own judgements. So be careful. Most lights out there have tried and true spectral outputs, but how effective are you delivering the entire spectrum required for your stage of growth?
Anyway, hope this helps. I can append more info if I forgot anything.
and look at your plants. You will understand.
