(Forgive me if this is terribly off-topic or circuitous. My ADD is kinda in overdrive today.)
(Not sure if this link is gunna work so if not:
doi:10.1111/j.1556-4029.2011.02024.x
The Effect of Electrical Lighting Power and Irradiance on Indoor-Grown Cannabis Potency and Yield )
These dudes are averaging a little over a p per square meter with plain ol’ philips HPS across three different light intensities. 3 week veg, 8 flower, ambient co2 only. They report intensities at W/m2 but after checking some references for the bulbs in question:
600w/m2 of philips Son-T = ~1000umol
so 270w/m2 should be around 500umol
https://www.waveformlighting.com/horticulture/daily-light-integral-dli-calculator
Plus a DLI / PPFD calculator says they’re between 20-45DLI. Even at the lower light intensity they’d probably be better off adding a lil co2 rather than more light. ~45DLI is 500umol@24/0 and 700umol@18/6. Granted we’re talking veg schedules, not flower, it applies to autoflowers.
(Addendum: Based on this photosynthetic efficiency chart 1200umol at ambient co2 will be, more or less, equivalent to 400umol at 1400ppm co2. That seems too simplistic for reality, so I would love if someone would prove me wrong.)
(These two graphs are part of this article.)