Grow Light Penetration is WRONG

The concept of Grow Light Penetration has bugged me for years. Until now I have not really understood what was meant by the term. There are regular comments in videos that low optimum hanging height = a grow light with poor 'penetration'. This has regularly been commented about my own ARAY LED Grow Lights so I am especially motivated to debunk this misconception.

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[timpage]

I just wanna say thank you Shane for your invaluable service to our community.

And to the hard heads. Shane can’t even legally grow cannabis yet his wealth of knowledge and service and contributions to our craft help so many maximize their grow space potential. Something should be said to years of contributing knowledge he’s shared with all of us. So many would still be lost in the vastness of bro science otherwise.

[Ledgrowlightsdepot]

Thanks for the video! As far as I understand it, penetration is not exactly the lights ability to push through leaves, but the difference in light intensity from the top of the canopy to the inside or lower part of the canopy. Higher intensity fixtures at a farther distance will push down farther into the lower part of the canopy assuming there is room (via trimming / defoliation) to do so. A light at, say, half the intensity and close to the canopy will have lower vertical penetration, but decent horizontal penetration. Growing in an open room with several fixtures will allow better vertical and horizontal penetration as the light comes in from several angles. Contrast this with growing in a tent with a single fixture: Vertical penetration may be good, but if the fixture is high above the canopy, the horizontal penetration will be low. If the fixture is lower, you are using a bar style fixture, and the plants are not too bushy, the vertical and horizontal penetration will be good. Overall, there are a lot of factors to consider with penetration and there is not a one-size-fits-all answer. -Erik

[garywillow]

I can't believe anyone who has watched your videos and listened to your knowledge, has any doubt that your lights are the business. Your integrity screams out with every video.

[Dodgerdoes]

You’ve done more for indoor growers than you know! Facts and information that are so useful to those who want to learn. Been watching you for years now.
Big Thanks!

[zumbaladin]

We must thank and salute Shaun's patience.
I never thought I could get that interested in lighting science since I started growing "lettuce".
Take care Shaun, and thanks again for sharing your knowledge (most people in this industry would just show off and pretend they sell the super duper never seen before LED technology with preposterous numbers coming off their foggy minds).

[laoluAD]

Love nerding out on this kind of knowledge, you can never know enough. It’s always nice to know why we do things, in this case defoliating. Helps apply it in ways that get better results. 🔥

[TxRedMan]

When I think about grow light penetration for LED’s, I am thinking about the amount of PAR on the edges relative to the amount of PAR in the center. Ian, (Shaun! I’m so sorry if I just got your name wrong) my first grow was in 97 with a horizontal HPS fixture I built when I was 15. I haven’t done any studies, but I will say that I noticed a significant difference in the size of lower growth when I stopped supplementing with the horizontal 400’s. That was 20+ years ago though. Also, where I am in the US, tents aren’t as common as you might think. Basically if you have a basement, it’s 50/50. Btw, you’re the reason why I have a Maxsisun running in front of me as I type this. My next light will be from you, we need to support those who are active in our community!

[Санчес-ят]

8:01 do you like the spectrometer Asensetek? Can you recommend it? How does it compare in terms of accuracy to Apogee?

[bobmckee]

Thanks Shane. You are spot on, as always. The concept of the top leaves being solar panels is helpful. Maximize the density of leaves at the upper canopy, capture as much light as possible means we are mimicking a natural outdoor grow environment that the "lettuce" evolved in over the millennia.
Your explanation of light penetration strongly suggests S.O.G. (sea of green) method in growing the crop.
Thanks so much for your clarity in helping us optimizing our grows. It is the best way to maximize yield.

[katrinachristopher]

Shane you are spot on. To contribute... I think there were a lot of older growers in this industry that were saying LEDs did not have the same penetration as HID lighting. With older LEDs this may have been true in a way, but certainly not as we have seen here by your poll. Early LEDs did not have the green spectrum intact. With that, there was a diminished activity in the leaf structures due to only shallow tissue "penetration" occurring when the light hit the leaves. You illustrated this perfectly with one of your slides. Once the light package went to full spectrum, and then later with the addition of Far Red wavelengths, LEDs came into their own as a viable option vs. HID. As far as mechanical penetration goes shade is what it is. FACT - If an area is shaded from a light source the light intensity will be reduced in the shaded area regardless of what lighting type is used. Again... Having your multiple source light fixture (bar type lights vs. single quantum boards) means that light is available from multiple angles which minimizes shade areas. It is truly the best possible solution. Now what I would like to consider is it better to remove the blocked leaves off the bottom of the plant OR is it better to take off large leaves to let unblocked light down into the Great Video!!

[greybush]

defoliation and stripping unproductive budsites is your friend no matter what light you're using. If you have limited overhead room in your grow area and want uniformity in light spread and less intensity and hot spots, use a bar style. If you just want to saturate your plants with intense light and can manage hot spots over your canopy raising the fixture within smoke overhead space, use board style boards. Prune and thin foliage for best "penetration"of light and maintain a hanging height of fixture to maximize light coverage on the actual bud sites. Leaves are like solar panels to collect photons for energy, but they block the photons from effectively reaching anything below.

[KapRowMeat]

light penetration is not the actual light penetrating the leaf, rather how much light reaches the bottom. more shade less light penetration / less shade more light penetration

[rmcnasty]

I tried adding migro pro to all 4 side walls, lighting the lower shaded part.
I had big sticky buds, down low. instead of small buds. If u have any old spare lights, I could use for my new, Grow tent Test Video. This is what I call full penetration. Thank you for sharing your Videos.

[nickbaugh]

Remember the phototron? I would like to know what you seriously think of the phototron or maybe an updated version of it with LEDs that has light all the way up and down

[patricknolan]

The next question should be: Is it better to have a full plant canopy closest to the light or to have some openings to help develop the upper middle of the structure?

Assuming you are hitting max useable ppfd, there might be an argument for creative pruning to let some light through the plant.

[sparkysmalarkey]

I trim the bud sites below the canopy but I keep the fan leaves. The plant will decide when it no longer needs them. It also provides dump sites for excess nutrients and other waste they accidentally consume.

[timturk]

Great video, once again Shane! As soon as you mentioned the topic, I remember the comment that caused confusion from the last video.
Excellent!

[redshedllc]

Thanks for the video always will like watching yours as opposed to many other channels on lights Bruce bugby is a really cool one though. But I would love to get your opinion and maybe a full video on photo periodic control. Utilizing much less light duration while getting comparable and better results. I use 6 hours on and 18 hours off for my flower room and so far I'm really impressed with the yield for 6 hours. For vegetation I use 12 on 5 1/2 off one on five and a half off and same thing I get really good growth plans are always praying no matter what and I'm just curious why people don't push this light cycle further. I know longer light cycle means more use of water and nutrients and electricity and your time but is it necessary? And in my opinion I don't think so at all. Anyways thanks again and would love to hear back

[jakebrake]

What’s really interesting is long wave and short wave radiation. I’m doing a grow from seed, using a 105w LED SMD panel light with dim ability through a MeanWell driver and Samsung LM301H/B’s. I’m using an oil filled radiant type heat source in my 2’x4’x5’ grow tent. Two plants, one was pinched at the 3rd-4th node, I’ve trimmed it up into a canopy of lollipops. It has 3-main branches after I removed the fourth one due to a first timer mistake. That side has been facing the radiant heat source, and it’s growing out a replacement stem to take the place of the fallen limb. Knowing that heat needs to be introduced in with LED grow lights, I suspect that what the plants are then able to benefit from, is that long wave radiation buildup in the soil, as well as the invisible heat from the long wave radiation. When she goes outdoors, that’s the side that I’ll face due-south in my northern hemisphere. That way, it not only receives the short wave visible light, but also the long wave infrared radiation that the hardcore HID crowd long for.

[andrej]

So your light has a recommended hanging hight lower then other lights because it is spread so well and other lights would underperform at such low highs?

So being able to hang it so low with same spread as other lights at higher hanging heights then in return icreases the efficiency?

Thank you!