LEDs in planted applications are typically measured using PAR
or Photosynthetically Active Radiation. Quoting a discussion of the topic on another forum, in regards to light level and PAR:
Low = 10 - 30
Medium = 30 - 80
High = 80 and up
light fixture manufacturers publish their PAR readings which make things convenient. Others do not. There are PAR meters that can be used to measure the PAR output.
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