Light itself

candela (symbol: cd) is the SI unit of luminous intensity. Power emitted by a light source in a particular direction (Total amount of light in certain direction.)

Lux: Amount of light landing on a surface (10m wall, 1m^2 surface, and measure it)

Lumens refers to the total amount of light a lighting apparatus emits. We represent lumens as L. (Like Horsepower)

The lumens unit does not consider the spread or divergence of the light being emitted by the device.

light for plants

Photosynthetically Active Radiation (PAR) : Radiation between 400 and 700 nanometers

Photosynthetic Photonic Flux (PPF) : The entire PAR light emitted each second by a light source

Density Flow Photosynthetic Photonics (PPFD) : Measures the entire PAR light that enters a plant every second (µmol/m2/s)

Daily Light Integral (DLI) : Calculates the entire light provided to a plant per day

How to compute DLI out of PPFD?

PPFD x 3,600 x Daily Hours / 1MM