Maximum / Optimal Lux or FC for LEDs and checking readings

lux / footcandles are the same scale or whatever.. essentially same thing without splitting hairs the "max" lumens you can provide differes due to varying CCT and other attributes of the light you provide. So, you'll have some trial and error, but when you find a happy zone, it'll be very similar in future. Lux/lumens will be proportional to intensity. so, if you measure 25k in center and 12.5k on edges, there is also 1/2 the actual DLI / PPFD / PAR light hitting the edges. DLI is best way to talk about this with other growers because it does not matter if size of garden is different nor different CCT and other differing characteristics of light provided. It doesn't even matter if talking about autoflowers and photoperiods which can have drastically different light schedules... it's apples to apples, which is why it is best way to talk about this. REad up on basics of Daily Light Integral, PAR, PPFD... don't need to memorize equations, just understand gist of it. key is that the energy we provide per 24 hours cycle is roughly the same maximum whether you provide it over 12 hours or 18. obviously the rate of photons is much higher over 12 hours to provide same energy as 18 hours of light, but if we count up the photons, it's going to be very, very similar. studies show the same dli at varying hours of light per day equates to same yield. some common sense is necessary here.. don't try to prove it wrong providing 1 hour of light per day, lol.. that'll defintiely burn the plant. but 12-20 hours? as long as you hit that upper crust of DLI relative to your environment (temp/rh/co2 dictate what the "max" is at any moment in time) you are going to yield as good as you can as far as what the light provides and ignoring all other factors for clarity. apps on phones will be much higher readings than with an actual lux meter device. the dedicated device (10 usd) does a better job only reading light from a perpendicular direction, where as your camera phone will also include more light coming from all angles. So, you may see 25-30k with a real lux metere then 50-75k with a lux app on your phone... no big deal.. these are only relatively proportional readings and don't inform about PAR/PPFD/DLI in any precise way. "photone" app conversts this lux reading (bc your phone is not a quantum meter not matter what app you load onto it) to PPFD. Since LEDs are very similar you won't be more than 10% off probably... unless using a blurple or light with an odd spectrum flux density. BUT, the app doesn't know if your light is 3000K or 4000K and that matters, so it'll always be off a bit because there is not a one-size-fits-all conversion factor. flip a coin.. photone or a normal lux app on phone... still just good for relative intensity and helping even out light intensity across your canopy, within reason. an accurte spec sheet umol/s value, the area that you cover and hours of use is going to more accurately guesstimate your actual DLI than any phone app. qunatum meters are 500 usd or so, and not worth the money.