Targeting PPFD and DLI

650 ppfd with 15 hours is 35.1 DLI. There's more than one way to get there. There are DLI tables for reference. 667 over 14h is only 33.6. It's proportional to hours of operation... algebra can get you anyhwhere else. Also, most calculate ppfd wrong or the app isn't clear or let's you do it the wrong way etc. PPFD can't be a single spot measurement. It's the amount light relative to 1 meter-squared. A single point measurement is only PPF or PPE. If you measure in ceenter your supposed DLI will be exaggerated. If you measure on the side it'll be understated. You need several measurements equidistant apart and same vertical distance from light - average it out and that is a good estimate of PPFD. But, this is not necesary. I only tell you if you have a compulsion to do it. That's not how you use DLI in this context. It is merely a ballpark starting point. From there you adjust based on how the plant grows. This also assumes a mature plant... ramping up with seedlings is its own process. The point is whether you start at 35 or 33, really doesn't matter... it's close enough and you don't decide max DLI... the environment does. if you have accurate specs from your light, which is not as often the case ass you might think, you can cut some corners and get a simalrly good ballpark to start with. totoal umol/s PAR production of light divided by area in m^2 (larger if less than 1) and that's your PPFD .. it'll be a bit of an overshoot, so go for "40" dli to start. This accounts for light absorbed or missing the plant as it spreads out. 35-40 dli is a good target regardless... in the end you still have to adjust based on plant growth and way easier than taking a bunch of precise measurements for something you cannot be precise about in a top-down manner relative to a home garden context. 200umol/s par focused on 0.2m^2 is 1000ppfd. 200 focused on 1.5m^2 is 133 ppfd. Common sense diode distribution required. This stuff assumes other aspects are in order. When you find an intensity that's dialed back from causing damage or stunting, you know you are at upper edge relative to local factors. If you have seasonal differences, you may find you can give more or less throughout the year... you can recognize and adjust for each season accordingly. Depending on climate control and ambient co2, you may be able to give more or less than you initially estimated. The plant's growth pattern will have the final say. You do not choose 'max' DLI from a top-down perspective. It is a matter of several factors that are not always consistent.