High Guys,
Cannabis has been legalised in Germany since 1st April 2024. Many people are wondering how this will affect our society in general and lighting design in particular in the future.
Greenhouse lighting is something special: plants obviously do not use light to see, but to photosynthesise. However, most photometric values relate to the visible light range between 380 and 780 nm, as assessed by human sensitivity to brightness. The effective spectrum of photosynthesis is completely different and covers the range between 400 and 700 nm.
For this reason, the values PPF (photosynthetic photon flux) and PPFD (photosynthetic photon flux density) are also specified for luminaires that are used specifically for greenhouse lighting.
So is the illuminance in lux meaningless for greenhouse lighting?
No, both values can be calculated from the luminous flux or illuminance:
PAR PPF [μmol/s] = luminous flux [lm] / conversion factor
PAR PPFD [μmol/s/m²] = illuminance [lx] / conversion factor
The conversion factor depends on the light source used. For a cool white fluorescent lamp, for example, it is 74, but there are numerous conversion tools on the Internet that will do the mental arithmetic for you.
The amount of light required will of course depend on the type of plant.
How do you deal with this issue? Do you calculate the photosynthetic photon flux yourself from the lux values? Which products do you use for greenhouse lighting, what role does greenhouse lighting play in your everyday life?