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Light: Difference between revisions
→Horticultural light metrics: Cleaned up metrics section
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== Horticultural light metrics ==
There are many different metrics that can be used to measure the intensity and quality of light for photosynthesis in the cultivar. These metrics are important for assessing if a source is sufficient but especially notable when comparing two different lights.
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=== PPFD ===▼
Photosynthetic Photon Flux Density: its unit is μmol/m<sup>2</sup>/s. It is a measure of light intensity within the [[Light#PAR|PAR]] range over an area per second. The maximum PPFD a grow light can produce is important to know before buying as well as the size of the area it can deliver that PPFD.▼
Light intensity is quantified by the number of photons produced per second. Because the number of photons is so large they are measured in micro-moles (µmol). One µmol is actually 602 quadrillion photons. See: [[Light#Measuring light intensity|Measuring light intensity]]
▲=== μmol/J ===
The light intensity a horticultural light produces per Joule of power it uses. This is a measure of its efficiency. At the time of writing, the most efficient LED package available is the [https://www.samsung.com/led/lighting/mid-power-leds/3030-leds/lm301h/ LM301H] by Samsung. It achieves 3.10 μmol/J @ 65 mA, 25°C. Note the efficiency will change depending on the temperature and current supplied.▼
=== Photosynthetic Photon Flux Density (PPFD) ===
unit: μmol/m<sup>2</sup>/s.
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unit: μmol/J
▲The light intensity a horticultural light produces per Joule of power it uses
=== DLI (Daily light Integral) ===
unit: mols/m<sup>2</sup>
The amount of light energy (photons) a plant is receiving every 24 hours. For example, if you used a light with a PPFD of 500μmol/m<sup>2</sup>/s on a 20/4 [[Light#Light_schedules|lighting schedule]] that would result in a DLI of 43.20 mols. DLI is generally the most useful metric of light intensity the plant is exposed to as it takes the light schedule into account.▼
▲The amount of light energy
Full light intensity from the sun in summer reaches around 60 DLI<ref>https://www.youtube.com/watch?v=ID9rE5JewVg&t=1170s&ab_channel=ApogeeInstrumentsInc. - Bruce Bugee Grow lighting myths</ref>▼
▲Full light intensity from the sun in summer reaches around 60 DLI<ref>https://www.youtube.com/watch?v=ID9rE5JewVg&t=1170s&ab_channel=ApogeeInstrumentsInc. - Bruce Bugee Grow lighting myths</ref>
[https://www.waveformlighting.com/horticulture/daily-light-integral-dli-calculator DLI calculator]▼
[[File:DLI equation.png|center|thumb|349x349px]]
== Horticulural light terms ==
=== PAR ===
[[File:PAR range.png|thumb]]
PAR stands for Photosynthetic Active Radiation: light within the range of 400 to 700 nanometers that drives photosynthesis. For reference, the human eye can see light between 380 to 750 nm.
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