thanks maurice that was super informative i didnt realize the huge discrepancy in T5 efficiency and agree that any one built as a grow light uses the cheapest shoddiest bulbs and ballasts
i was looking more closely at the CMH numbers, my cmh ballasts (hydrofarm) dont draw 355W from the wall, more like 335-340W at the wall, and is a square wave output which makes the output more efficient. on a bulb basis alone, the cmhs are almost 110 lm/W initally and maintain 95% of this after 2 full years of flowering. with a ballast around 93% efficient youre up around 99 lm/W of high-cri light at mean bulb life after 1 year of use
View attachment 3992841
i was digging a bit into GEs product data, and while i do see bulbs that are 4800 lumens that is initial not mean. traditionally fluorescents drop off steeply and then hold (as opposed to CMHs which are more linear). So the 4400 lumen mean data GE provides is probably more accurate. i dont know if the programmed start ballasts help with this lumen maintenance issues
View attachment 3992866
so using the 4400 mean lumens it seems that CMH and the best T5 are right in the same wheelhouse
Whether lumens translates into usable PAR is another story. CMH has lots of green light but the spectrum is more uniform than T5 with a green peak centered wright where lumens are measured. also worth consideration with the "green inhibition" noted in this thread
would be a good side by side of one of the more efficient T5 setups vs a 315. what do those HQ bulbs and ballasts cost typically?
obviously DE HPS and LED with system efficiencies of 130-160+ lm/W are in a class of their own
that HQ T5 info should get out there. easy retrofit of ballast and bulbs into the shit ton of fixtures out there, and the spectrum of fluorescent (and mellow uniform lighting) is a proven performer for rooting and early veg
there seems to be somethign about the CMH spectra though. As ive mentioned ive seen people hit 1.4 GPW with rooms of 315s, ive never seen that with T5s (ive also never seen anyone using those super efficient T5s
heres a link (a few years old) where GE claims the T8 is even better (pg 23). im sure this info is somewhat dated
https://ewh.ieee.org/r3/atlanta/ias/Whats New in Lighting w_ LED.pdf