Everything I have read says a ppfd between 800 and 1000 is good for flowering well with my 600 watt hps lamps on super lumens setting at 12 inches shows like 1800 ppfd or more some of my tops are 12 inches away or less while the lower canopy is 18 to 22 inches below the lights the temperature is 79 f in there anyways I guess I am pushing the envelope but I see zero stress at all No taco leaves no discoloration nothing so I guess now the stretch is done I will leave them at this height keeping a close eye on them but very surprised they can handle so much light I gat one reading of 2100 ppfd lol and they are absolutely loving it
Back in the day ppfd was never mentioned and we survived. I just try to read the plants and leave it at that. I have a lux meter. I honestly feel that is enough but these tech junkies growing today have all sorts of charts and methods going..lol. Watch your plants and use your gut. Your grows have been consistent and massive. I'd stick with what ya know. Hey I'm not knocking ppfd or any other means of light measurement. They are simply tools.
you wanna talk photons with HPS you gotta speak in Lu(lumens) as theirs no comparison ppfd/U-mols is only for LED's, anything above 1000 u-mols you better be using C02 to eaze the pain from memory the best return for your 600w hps is 14-18 inches above the plant tops set by my temp gauge for 25c/77F good luck
Indica and sativa react differently to certain light spectrums... especially to UV-B or UV-B supplemental lighting Sativa is prone more to burning then Indica.
One thing to keep in mind is that hps emit significant infrared light radiation as opposed to leds that typically emit little to none. Its worth it to measure actual leaf temps. Later in the grow you may volatilize many terps if the leaf temp is too high. The best way to measure leaf temp is with an infrared ‘temp gun’ or FLIR. The temp guns are cheap now a days, like $25. Cheers Os
see i didnt know that about lumens lol i am behing the times on technology i will go in there right now and read lumens hold on lol ok the highest up tops are looking at 110,000 and the lowest around 75,000 and now i am blind lol
here are some convertors I've used in the past in particular Lux to PAR https://www.waveformlighting.com/horticulture/convert-lux-to-ppfd-online-calculator others https://www.waveformlighting.com/horticulture/ it might be a good site for DIY leds?