What kind of lamp should I use?

What bunch of numbers said 💯

what he said.

The caluma force 320watt spec sheet is a giant load of bullshit. They misrepresent umol/s based on highest value ontheir par map, which is retarded and wrong. that would mean the efficacy is 3.8 range not 2.7, which is impossible because nothing is that efficient on the market. Also, it's using the 2835 diodes, which are not as efficient as the lm301 diodes. There is a huge variance in efficiency among the lm281 lm283 et al 2835 chips... some are really shitty efficacy, the B+ pro is maybe 10-15% less than the lm301. So, their spec sheet cannot be trusted. you'd need to look into the exact diodes used, how hot they are running them (watts per diode) then compare to a real specification sheet on samsung.com. anything above what they were tested at will reduce longevity and efficacy further from spec sheet listings. Ahh.. further down the math adds up better but they definitely do some sketchy things in their spec sheet. 2.65umol/J x 320 = 830umol/s ---- The GC Euro 250 watt At least the numbers they put onthe spec sheet make sense -- 250w x 2.7umol/J = 675umol/s Whether or not that is accurate, again, you'll have to get the diode model number and calculuate how many watts per diode they are running at and then compare to the real spec sheet on samsung.com for that diode model number. Anything above testing paramaters will significantly effect longevity and efficacy. ---------------- lying on a spec sheet for a grow light is the common practice, but still a bad omen. There are 'good' lights with bullshit spec sheets. Also, the major difference in quality in grow lights is their longevity and efficacy. Out of the box, even an inefficient light that provides the proper DLI to the plants will have good results. They merely die faster (the diodes, not plants) and create more heat. The latter of which can be a benefit in some contexts, but reduced longevity is 100% a negative. ------------ Final conclusion, assuming the umol/s production is accurate, which is not a sure thing. 830umol/s vs 675umol/s of PAR. One is simply stronger and can cover a larger area of plants while providing optimal DLI. The following are rough estimates.. local variables will impact exactly how much you can give to a plant. so "10.375" is just a ballpark and there will be some give or take due to local variables. 12 hour operation and providing ~37DLI based on output of light (will be less, but it is overshooting the DLI target to start, which makes up for photons lost to radiance or absorbed by walls): 830 / 80 = a little over 10.375 sq ft of coverage .. just under 1m^2 ... 675 / 80 = 8.4375 sq ft of coverage... a 3x3 is fine for this light, too. If you grow autoflowers, exclusively... 18 hour operation (proportional to change in hours, all other factors remaining the same) 10.375 * 1.5 = 15.56 sq ft 8.4375 * 1.5 = 12.66 So, the size of your tent may make the choice for you. On paper both lights say they are roughly equal efficacy. They are both quantum boards. You'll have to do the grunt work and compare testing specs for diode manufacturer to the light manufacturer's spec sheet to figure out if the information listed has any integrity. That might impact your choice too. The closer the light runs the diodes to samsun specs (or osram or bridgelux etc) the more you can trust any high-end numbers, like 2.7-3.0 umol/j efficacy... only the well made stuff that doesn't cut corners hits those numbers.