Light %

The stage of a cannabis plant is a handy guide but that's all. Cannabis is a light whore loves light. Give you plant as much light as it can handle and it will grow incredibly well.

The XS-1500 Pro will put out quite a bit of light and, at 16" hang height, you're at about 600µmol. I use word "about" because I don't have a PPFD map for that height so I'm looking at the one on the Amazon listing and the info here. 600 is considered the minimum amount of light that you should give a plant in flower. Why? Because.

That's the number that I think Bugbee provides and I know that DeBacco (You Tube) states that but DeBacco isn't a researcher. He repackages a lot of what Bugbee says but I haven't read anything of his that's not in synch with Bugbee and others.

An excellent source for this is from Bugbee student, Mitch Westmoreland, who published a couple of YT videos this Spring with some of the research that he did for his PhD. Every grower should watch at least one of his two videos. He lays out his research very well and it's pretty simple 0 give you plants at much light as they can tolerate with ambient temps up to the mid-80's. Do that through veg and into about the second week of flower. That will allow the plant to build out its infrastructure. Once you're in about week two of flower, if you want to maximize secondary metabolites, keep the temperature at the top of the flowers <=78°F.

OK, great info but it doesn't answer your question, because it depends on the grow. If you grow is "firing on all cylinders", you might be able to go to 100% and drop your hang height to 12". Per cocoforcannabis, that's going to get 950µmol± on your plant. That's quite a bit light but cannabis will handle more than that in ambient CO2.

On the other hand, you might drop the light to 14" and get canoeing of your leaves. If that's the case, you should check your grow and see what's not set up right. VPD could be off or not enough//too much wind in the tent or nutrient level too high. It could be a variety of things that, if they get adjusted, can allow you to feed your plants better.
But what I mean is when to I turn up the light% or woukd I even have to right now its at 50%
 

Delps8

Well-Known Member
Is ppfd next to the names and the lux it is or somewhat the top like the 10,000?
Lux values are the "10,000", "20,000" etc. in the column headers. The PPFD values are in the body of the table.

For the XS-1500 row, 10000lux is 145µmol. Just run your finger across that row and, each time you hit a new column, the table shows you the corresponding PPFD value.
 

Delps8

Well-Known Member
But what I mean is when to I turn up the light% or woukd I even have to right now its at 50%
That's not generating much light.

"have to" - there's no "have to". It's completely up to you. Cannabis will thrive at very high light levels but it will also grow well at modest light levels.

If your hang height is 16", a well setup grow will use 100% but the only thing I know about your grow is that you're giving it 50% of a Vipar at 16" so it might not be the case for your plants.

If I assume that your grow is in decent shape, I would advise you to turn up the dimmer dial from 50% to 70% and then watch your plants. If they can't tolerate that change, turn the dimmer back down and figure out why they can't tolerate that amount of light.

I sense some timidity/lots of caution. Fair enough. If there's too much light, the plants will tell you in a few minutes. They'll curl the edges of the leaves or take other action to get away from the light stream. No big deal. Just turn it down a bit.
 

Mumbeltypeg

Well-Known Member
That's not generating much light.

"have to" - there's no "have to". It's completely up to you. Cannabis will thrive at very high light levels but it will also grow well at modest light levels.

If your hang height is 16", a well setup grow will use 100% but the only thing I know about your grow is that you're giving it 50% of a Vipar at 16" so it might not be the case for your plants.

If I assume that your grow is in decent shape, I would advise you to turn up the dimmer dial from 50% to 70% and then watch your plants. If they can't tolerate that change, turn the dimmer back down and figure out why they can't tolerate that amount of light.

I sense some timidity/lots of caution. Fair enough. If there's too much light, the plants will tell you in a few minutes. They'll curl the edges of the leaves or take other action to get away from the light stream. No big deal. Just turn it down a bit.
Do plant reactions to light really happen in minutes? I didn’t know that.. that’s interesting, I have always adjusted and left overnight for reactions thank you I’ll have to play with this.
 

larrypizzimp93

Well-Known Member
If it’s 150 watts just understand the buds are gonna be small and not as dense. Especially if you have a plant with bad genetics. But I would keep it around 12 inches from top and if the top is yellowing, raise light (that’s light bleaching)
 

Delps8

Well-Known Member
Do plant reactions to light really happen in minutes? I didn’t know that.. that’s interesting, I have always adjusted and left overnight for reactions thank you I’ll have to play with this.
I've had a couple of instances of my grow light going to 100%. In each case, it was at that level for about 30 minutes before I noticed it. First time was when I switched on the second rocker switch on a Mars SP 3000. I didn't realize that I'd hit that button and, apparently, it bypasses the dimmer and sets the light to 100%. The other time was when the dimmer on my Growcraft failed and set the light to 100%. The Mars went to <1100µmol but the Growcraft went to almost 1300.

The only way I knew that there was an issue was that the temperature in the tent went up rapidly and since I have a Controller 69 in the tent, I could see the temp spike.

In both cases, the reaction was very rapid but both cases weren't just "a little bit too much light".

The leaves didn't canoe. Instead, they rotated around their petiole, similar to how a Venetian blind turns the slats. Fortunately, the leaves that were impacted started rotating back to normal orientation within about ½ of turning down the light.

One grow which got just a little too much light had a cola that bent, right near the top. It never straightened out, though.

Perhaps the issue that I hit was because the plants were getting gobs of light more than they could handle vs maybe just 100 or 200µmol more than LSP to which they might have reacted by canoeing. Don't know. Twice was enough.
 

Delps8

Well-Known Member
Yeah sorry, typo.

Soon as you flip to flower 100%
And drop the light.

At 12" that light is putting out <900µmol which is where cannabis is quite comfortable. The various charts that show giving cannabis 600-800µmol in veg - or worse yet, the silliness that the Photone site talks about - aren't research based. They're very conservative recommendations and/or ignorance.

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I believe that's one of the reasons why Shane at Migro sells lights that put out modest amounts of photons. It perplexed me for a while but I saw it as a savvy business move - lower powered lights are cheaper to manufacture and most growers don't know the difference. I can understand that as a business strategy. But Shane also has done videos about "How much light does cannabis need?" and his recommendations were not in line with published research. The guy is an EE so he's got some smarts so something just didn't set right with me.

Then I watched Shane interview Bugbee about light (it's on YouTube). When Bugbee says get plants to 1kµmol, you can see Shane just stop. To me, he looks, honestly, shocked but he recovers and asks the question again, expecting a different answer. Bugbee comes right back saying do the ton. Shane expresses his surprise and moves on to another question.

OK, he honestly didn't know. Now he does. And he hasn't changed the design of Migro Aray lights.

The OP can leave his lights at 50% and will have a happy plant and cop a few ounces. On the other hand, if he turns up the dial, he'll probably more weed. For me, I'll be damned if I'm going spend 3 months of my life to grow 4 ounces of weed. I'm 67 years old (68 in a few months) so I don't have that many more grows left. Plus, I've put a shitton of money and time into my equipment and processes so, for me, if I don't get a pound out of a grow, I consider it a failure.

Again, it's how the grower wants to do it. I just hate to see people putting their heart and soul into a grow and getting a couple of baggies worth when they can lower the light a few inches and end up wondering "what do I do with all this weed?"


Two plants, one grow.

I'm not saying a grower will get this kind of yield just by turning up the dial but I am quite sure that if a grower doesn't turn up the dial then he won't get this.
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