Along this subject of PPFD and correlation to yields and finish times. I just did a run in my room with a total of 600w of 3590's at 1400ma.
I have 2 different models of Tasty LED T2-1400's. The back of the room had 2 units with 3 COBs each @150w each covering off 3 x 3.5', or ~28w/sq. ft. Front of the room had 3x T2-1400 but older models with 2 COBs @50w/each or 100w per bar.
The front of the room under 3x 100w were spread out over 3 x 4.5' or ~22w/sq. ft.
What I've noticed is a couple of things.
1) The one's at 22w/sq. ft. took about 1 week longer to finish than normal for the phenos in that space
2) The same one's (22w/sq. ft.) produced some huge colas and nice weight/density, even under less light
The one's at the back running at 28w/sq. ft. seem normal, very nice production/terps/frost and will be pulled in finish times that correlate to the phenos I'm running there, no extension of the cycle.
Questions as I'm not a COB head, just like to grow shit but do pay attention to little details like this:
Do my observations make sense to anyone who actually knows what they're talking about? lol
Is there a correlation and even better a calculation using PPFD or w/sq./ft. that would correlate and affect things like finish times or yields?
Seems to me I saw a post somewhere about something similar to what I just observed but can't find any references or calcs out there.
Cheers...