I am quite sure I can grasp the concept, I'm just not that scientific in my grow. (yet). I did look online for a PAR meter, they ain't cheap. So it looks like I won't be getting one anytime soon. It would appear the 35,000 Lumen of the T5's is fairly optimal for my space and strain, though I'm sure it could be tweaked for even better results.
The HPS lighting is attractive to me in regards to total Lumen and penetration, but I just can't deal with the heat. It's already been a problem in the winter, I'm going to have to revamp ventilation for spring and summer.
Then again....I do have a greenhouse.
Hmmmm....a 3rd in the comparison testing? Mother nature against the T5's and HPS? It would be interesting to see if the outdoor one's would stretch like the original mother instead of being Stumpies.