Yaild to expect of a 600wpro Zeus. All diled in with troll master / co2 just normal

if maxing out DLI for typical ambient co2 conditions and controlling the climate fairly well, upgrading the light won't do anything beneficial, unless it's a more efficient light at which point it might save some watts. DLI and a controlled climate dictates yield. Once you are providing 'max' DLI relative to local variables, you can't improve grams per sq ft. That is the ceiling of the ambient CO2. If growing heavy-yielding clones, you can shoot for 70grams a sq ft, but with genetic variety of seed, 50-60g/sq ft is about all you should hope for more times than not. You hit the genetic lottery with all of your seeds and you can exceed that, but don't expect it. grams per watt depends on efficacy of the lights. 2.6umol/J for your lights is slightly below top tier, but probably not worth the small wattage savings to upgrade. 2.6 to 2.8 is only a 7-8% difference in watts to produce same umol/s PAR. you might find a 2.9umol/J light,but anything advertising higher is likely massaging the numbers.. only using the absolute best high CCT chips, which really shoudln't be the majority of any good grow light. Warmer CCT have lower efficacy. the "3.14umol/J" you often see is exclusively for the 6500K LM301 chips.. and the most expensive binning process. You can verify all of this on samsung.com spec sheet for LM301 diodes. Always trust that info over light manufacturers that lie through their teeth more often than not. Temp, RH and ambient CO2 dictate what "max" DLI is for your particular garden. About as high as you can go is 80-85umol/s PAR per sq ft. This will result in a ~40DLI over 12 hours of operation. Can a plant adapt to ahandle more? Sure, but it's not going to improve yield unelss you have an unusually high CO2 level in that area. Even 40dli is probably too high 99% of the time. It's just a good spot to start, then dial in power based on observing plant growth or damage that results. From Lumatek: "PPF of 1570µmol/s " -- holy shit, Lumatek uses the correct vocabular, points for zeus. Really should say "PAR" after that umol/s but that's fine. They also seem to give accurate specs, which i consider an excellent sign from any manufacturer. It makes them unique in a good way. 1570umol/s / 83umol/s/ft^2 = 18.9 sq ft or 1.76 m^2 -- This is a target of 900 PPFD. This assumes the frame allows for proper spread of light to cover such a footprint. "Bar" style frame tends to spread out further perpendicular to the bars, so you get a bit of a rectangular light footprint as opposed to a square shape. this is math for 12 hour operation. If growing autos, it's proportional to hours of light. So 18hour operation can cover 150% of that area. You'd obviously have to hang it higher to get enough spread of that light... it'd still add up to the same DLI but over 18h instead of 12h (this is the key). Or, you want to run at 67% power for 19sq ft during vege (18h) and when you go to 12/12, run at 100%. If you cover a smaller area, you'll want to dim a bit from there.... again it'll be proportional to change in area, too, ceteris paribus. You clearly have a larger than 4x4 area and more than 1 light... This adds a wrinkle as you get some overlap from the array of lights. You can still figure each one can cover up to 18.9 sq ft, give or take (most likely a bit more as i said above, 40DLI is probably slightly too high of an initial target). A klux or ppf app can help space out the lights for optimal resulting light intensity between the frames. 2 of these 600w lights can cover 38q ft, so unless you have a larger tent than that, no need to upgrade. Even for greater efficacy, it'd take too many years to recoop the costs to make that a good choice, because your lights may not be top of the line efficacy, but they are very good efficacy... Even if heat is a concern, it would only make a half degree difference or something small like that. Greater efficacy does reduce heat added by lights.. but going from 2.6 to 2.8 or 2.9umol/J isn't much different in that regard. read up on DLI (daily light integral) - the wiki is sufficient. LEarn how hours and area are proportional (or inversely proportional) to required umol/s PAR output from a light. You don't have to memorize the math or convert to moles per day.. a DLI table can do that for you - reference hours of operation and PPFD to get DLI. Do understand the gist and the relationships, and sizing a light to an area is easy as pie. Everything i said can be verfiied by reputable source material. None of it is opinion. "Max" DLI does vary due to local variables, so there is always some fine-tuning to do. It is just a good starting point to minimize how much you need to adjust from there.