knna

As i said in my first post, the sheet refers to radiance, but i suggested it can be applied to irradiance, wich is what we want to know.

Ill explain how to do it. First, we need a luxometer or photometer to measure lux (sorry, at the moment, i dont use footcd). Then, we need to convert it to PPFD.

The conversion factor is obtained from PPF/klm data. We need to convert lux to PPFD, so we need lm/PPF conversion factor. Divide PPF/klm by 1000 (to correct to lm), and obtain the inverse (1/x). That is the conversion factor. Divide lux reading for it and u obtain the PPFD value (same process is valid to PUR).

Example: You are using Fluora lighting. Its PPF/klm value is 24,618.
Divide it by 1000=0,024618
Obtain 1/x =40,62 wich is the conversion factor.

If u had a lux reading of 4000lux, divide it by 40,62 =98,47 microE/sec reaching the plant.

Another example: a pure HPS, like Phillips SonT Plus. Its PPF/klm value=12,27 /1000=0,01227 1/x=81,5 conversion factor
20000lux=245,4 microE
40000lux=490,8 microE
80000lux=981,6 microE
To reach the saturation point (i use the similar tomato, about 1200microE)
1200microE *81,5=97800lux si the max light density with this bulb.

I upload a pic of a botany study, wich estimates the conversion factor from lux to PPFD of various light sources. A generic HPS with a 1/8" plexiglas barrier have a conversion factor of 83. So i think the sheet have a reasonable error margin.

PS: Ive notice its the same multiply lux readings by PPF/klm /1000. But the 1/x value remains more significant to us, mere mortals.

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