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Ppfd

HiddenMessagestarted grow question 2mo ago

I use the photon app for ppfd estimates. I also use a taped piece of paper as the filter. I’ve typically had ppfd around 900 for veg with this technique. For the hell of it I wanted to see what outside sunny day was like.Ppfd was 1200in tree shade-2500 sun. Could I match that?

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00110001001001111Oanswered grow question 2mo ago

That app is a Lux meter in disguise. It converts lux to PPE, not PPFD. A single point measurement is PPE or PPF. PPFD is average PPF over entire area of coverage and realtive to 1m^2. When factored with hours of operation, you get DLI, which is what matters. This is th emetric that is an apples to apples comparison between gardens and the only way to discuss this with consistent results. DLI is DLI is a rose is a rose regarldess of hours of operation or size of garden. If the app can take the characteristics of light and adjust the conversion factor relative to the RBG ratio at hand, it'll be incredibly accurate. If it is using "1" conversion factor, it'll have some error for sure. Any deviaton from the RBG ratio from the stasndard for "Lux/lumens" will cause error in the conversion. Now that grow lights are all within a fairly small range - that curve showing different intenstive of red, blue and green wavelengths - the conversion can't be too far off. You'll see more error in a blurple light's reading than more modern LED grow lights. Varying CCT will cause error in the conversion because it changes the ratio of RBG. Think they even say it has a +/- 10% or something like that? think it's in the fine print. Consistency is key. That still makes it useful. The readings are consistent for that 1 piece of equipment and any other light with exact same properties -- same cct, same RBG ratio etc etc. You stil have to adjust for different climate variables, but, if you find "X" PPFD provides the growth pattern you want, then it won't be far from that measurement in the next grow cycle... temp, rh% and genetics are a factor, too.

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m0useanswered grow question 2mo ago

I agree with numbers and greenaf, they tend to know their shit when talking about light. The apps are close if calibrated but they are never calibrated, and inf order to do that you need a real quantum par sensor or a light source that's so perfect it keeps its output at a standard.

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greenAFanswered grow question 2mo ago

I would just use the app at a reference its not actually measuring the umol, but if calibrated it close enough to use as a guide. Every one has there own way, i run high ppfd at atmospheric C02 and get great results and big yeilds, not to say its as simple as higher ppfd higher yeild. I range 1000-1400umol in flower, I have an actual ePAR meter and run my lights close. I'm still fine tuning but getting results i love so thats what I am going with. If you want to deep dive and nerd out here is some info https://pubmed.ncbi.nlm.nih.gov/34046049/ https://pubmed.ncbi.nlm.nih.gov/39409645/

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MrCoffeeanswered grow question 2mo ago

Unless your running Co2 i would not recommand more than 1000 ppfd at 12/12. That would give you around 45 DLI which is enough. More than that you will start stressing them.

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00110001001001111Oanswered grow question 2mo ago

You can but it'll be a waste of electricity. The plant can only make use of a certain amount of light per day. This 'maximum' is relative to several variables, primarily atmospheric CO2, but also temperature and RH%. This is not something people can circumvent. how much you can give is dependent on the above variables and anything above that the plant will merely adapt to mitigate the excess. When a plant is grown outside or inside, it adapts to the light it gets. In order to avoid damaging itself, it'll have less dense chlorophyl in the leaves. Just because it is sitting in 2500PPFD does not mean it can actually make use of it all. It merely tolerates it. this is math and plant biology, not an opinion.

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Ultravioletanswered grow question 2mo ago

Yes, but it takes alot to maintain the water burn. Need a pot big enough to retain enough water based on how often you can spend time with her. I done same thing when I got mine I took it outside on a summers day and it was reading 2-3k ppfd, I was like how on earth does a plant survive that all day! I can run about 2000+ppfd for 4 hours per day to illicit antioxidant response acclimation. Even then plant will show wear n tear. Takes serious equipment to keep cool and a decent hvac setup. Absolutely possible, real challenges begin when she gets big, sheer volume of water needed to maintain cooling is annoying. Bit needs must. Focus study on NPQ, Ascorbic acid and Zeaxanthin.

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ATLien415answered grow question 2mo ago

I have a background in physics and I am not knocking the photon app but I would be hesitant of any tools for measuring light output that isn't an instrument designed for solely that purpose. I have heard that modern phones are making the apps really good at this... I'd prefer to get a few dozen small panels of the same surface area and experimentally derive the values but at that point I'd just refer to manufacturer values. Are the apps really that accurate these days???

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