I have this one in my 3 x 3 and love it!
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Even though they represent two different things, the math works out roughly the same when you substitute “watts” for “joules”
So, if your like me and don’t understand all the “science jargon” really well then you can say you are looking for two micromoles per watt.
So on a 300 watt light you will have roughly 600 micromoles if you have a light that is 2umol/joule
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A 5 degree swing max is suggested.
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Thanks, I have the platinum p300 has PAR ratings on their site, powerful, not sure about the 2umols/j tho!
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Platinum is on the higher end of the “blurple” market however it is still common practice for blurple MFGs to not put in the umol/j in their spec sheets.
I went to platinums website and could not find it. Based on my experience with lights I wouldn’t grow more than one plant in an area no larger than 3ft² with the light you have
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Find out what the PPF is (maybe from manufacture) and divide that by the wattage and you get your umol/j , Happy Growin !
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Yeah pretty much what I am doing I can get more plants in, but right now I have only one Purple Urkle S1 which is scrogged 
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Hey what’s up fusiondesigner ? When I started growing indoors the leds I started with were advance platinum. In my opinion at the time they were the best leds out there. Plus they offer a 5 year warranty.
I started out big by throwing down at least 50 watts per s/ft. Cause I didn’t want to have any problems.
But when I built my lpa systems. I wanted to make them 3x3 and then buy some leds with a foot print of 4x4 or 5x5 in flower. That way I would have one light over each system.
So I purchased a few leds that the mfg. stated had a foot print of 5x5 in flower. Which it did.
But the fixture it self was only 18"x18’. So right at the start when I started growing with these systems I noticed that the units that were not right under the fixture were only getting half as tall as the ones right under it. The par dropped so much, it was crazy.
At the time there were no led mfg. offering a led with a fixture of 3x3. So I had to built my own.
Anyway I just wanted to give you and anyone else something else to think about when you go to purchase a led.
Take care…ASSOG…
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A joule by definition is a watt per second. The only reason you see it used is because we measure light per second. I know you weren’t the one asking, but I’m being lazy because you had the easiest comment to quote lol.
Umol per joule is the same as saying ppf per watt per second. The only real difference is that watts are typically measured on an hour scale. A 1000 watt hps light consumes +/- 1000 watts per hour. So outside of being a nerd on technicalities, using joule is less typing and leaves no further breakdowns in math to compare lights.
Going back to the other questions/statements, if you have an accurate photon efficacy you can size your lights to hit recommended DLI levels. Much better than a dated watt per square foot measurement that is based on older tech where just about every light had the same efficacy.
Using some cheats that I picked up along the way… On ambient co2 you’ll hit recommended DLI with a ppfd average of about 600-800 umols per second on 12 hour light schedule. Ppfd average is nothing more than total total flux over area in m². So, if growing in 1m² space you’re looking for a total radiometric flux close to 800 umols per second to hit point of diminishing returns. If your light runs 2.0 umol/joule, that means 400 watts would get you there. If your light runs 2.5 umol/joule, then 320 watts will do it. It’s probably more complicated than I’m explaining here, but so is each individual growers needs. Some people need to pull every gram out of space, others need to make sure they are running as efficient as possible.
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That’s exactly what I was trying to say its just my words aren’t quite as elegant as yours 
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You mean except for when I insist on single thumb typing, and all of my a’s end up as s haha
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So anyway I think the two main factors, other than providing enough of the right photons, in bud density are:
- genetics
- environment
Keeping temperature and humidity in the right ranges during the different stages of the plants’ lives is critical, IMHO, to achieving optimal results. But even perfect lights, temps and humidity isn’t going to fix bad genes. If my plant isn’t transpiring properly, I feel like I have no idea what’s going on with nutrients and can’t really identify and correct deficiencies or lockouts properly.
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