Originally Posted by Hookahhead
Awesome thanks, just the kind of info I was looking for! Do you happen to know the name of that study the graph came from?
Sure bud, here you go:
(In case the link dies in the future; THE PROPAGATION, CHARACTERISATION AND OPTIMISATION OF CANNABIS SATIVA L AS A PHYTOPHARMACEUTICAL (Potter 2009))
It's a long one, but just CTRL+F for "5.13." and you arrive the relevant chapter with the second result
The whole thing is a great read
edit: I can point to a possible criticism; namely that the light intensity in their experiment is not nearly at typical indoor levels. Who's to say the increase is the same at "pushing it" levels of light? Anyway, in my own timelapse I can see that with 13/11 at about 700 PPFD w/o CO2 the plants don't start to droop for sleep until the very end of the light cycle, which tells me the extra time is not wasted.
The reason I started with 13/11 is because I looked at some sunrise/sunset information of different places in the world. I'm surprised people even stick to 12/12, when they go to such extremes to increase yields in other ways.
Also there are non-cannabis plant studies which show that a lower light intensity* over a longer photoperiod gives better results than higher light intensity* in a shorter photoperiod. (obviously equal DLI in the end)