Plant lighting and Penetration, what does this mean exactly?

[Icemud]

I thought this would be a great topic of disucssion....

When talking about plant lighting....What exactly is Penetration?

I see this word on just about every plant and horticulture grow light advertisement, saying things like "increased penetration" or "best penetration" or "more penetration than..." but really what does this mean?

I mean things like lumens, Umol, lux, watts, are all quantifiable measurements for a specific purpose, but when I googled penetration I found a bunch of adult sites, but nothing to do with plant lighting or a measurement...

So this leads me to ask...What the heck are all these light manufacturers talking about? Is this even a valid statement, and how can one measure it"????



As far as my understanding, we could be talking about 2 things here.... light penetration through the canopy, and/or light penetration through the leaf to reach the photosystems (total light minus reflected light)...

??

If the word "penetration" was speaking in regards of penetration through the canopy...then I don't believe 1 light vs another light in the aspect of power usage is going to have much to do with anything. Lets say you have a leaf, and a 400w light above it vs a leaf with a 1000w light above it... is the shadow going to increase, decrease or stay the same if all other factors are the same except the lights wattage? I would assume that he shadow would stay the same size...so how his one light having more penetration in the canopy than the other??? I don't think they would...

Now using the same example... you have a leaf and a 600w HID light above it vs 2x 400w HID lights positioned above the leaf, but also set apart from each other...

Well according to all the Lighting companies...a 600w HID must give more penetration than 2x 400w HID lights right??? 93,000lumens vs 84,000 lumens?? Well according to most light manufacturers they would say, yes, more lumens is equal to more penetration...But when you look at it... if light is coming from 1 point source vs 2 offset point sources, there is going to be less shadowing with the dual point sources, therefore less shadow, more penetration because of the mutiplue angles the photons are traveling from 2 light sources... So in this case, 2x 400w HID would have better penetration than 1 600w HID right.... I would assume this to be correct.

So what is the deal with the term "penetration" and why is it so loosely thrown around my lighting manufacturers without any definition to what they are talking about, and no quantifiable measurements??

I would love to hear everyone's input, including all the LED sponsors and HID sponsors here....Lets clear this definition up and find out what these companies mean when they say.... better penentration..

 

[Graytail]

Good subject.

There's something else I've always wanted to have a chance to bring up. The closer the light is to the tops, the less penetration there is - kinda counter-intuitive.

If it's one foot from the tops, at 2 feet (one foot of canopy) it loses 75% of its umols.
If it's 2 feet from the tops, it doesn't lose 75% until 4 feet (two foot canopy).

Those numbers aren't precise, but it works for the example.

So more light, spread out, and farther away, is probably best for penetration.

 

[Hosebomber]

Penetration (when I use that term, and how it is used in artificial lighting) refers directly to the PPFD available at a given distance after the calculation of inverse square and lens/reflector coefficients.

Hope that helps.

 

[Icemud]

Penetration (when I use that term, and how it is used in artificial lighting) refers directly to the PPFD available at a given distance after the calculation of inverse square and lens/reflector coefficients.

Hope that helps.

So generally speaking when these companies are saying better penetrations, they essentially have more parallel light photons emmited from a point source via reflectors/lenses/collimating lenses. (more throw) or a more focused output..

It just to me doesn't make sense to use though as a plant lighting term. For example a long HO Florescent emitting the same Umol as a HPS would have better penetration because its a soft light vs a hard light thus limited shadowing and more leaf surface area touched by photons.

So even though by your definition of penetration the HPS would carry further or have more throw due to the reflector and wattage dispersed over a lesser sized light source, in my example above, the HO Florescent would actually have better canopy penetration if given Umol was equal in both lights because the light source is emmited from a larger surface areas, with more angles the photons are emitted.

This is why I wanted to bring it up because it seems like one of those throw around terms that is sort of meaningless in a way. So is penetration better when used in the terms of focus or light throw, or is penetration better when looked at is reduced shadowing and more leaf surface touched by photons.

Either way, I always appreciate your knowledge Hosebomber, and I definitely like how you answered it, but its still confusing to me as to why one would say better penetration when in actuality focused light has less canopy penetration from a single source as splitting the wattage between 2 light sources offset from each other.


Another way I have seen it referred to in a abstract was the difference between PPFD reaching the top of the canopy vs the lower canopy... which then would go along with more of the point source vs offset light source idea...

So it still has me wondering... what do they all mean, and why is it used so openly (penetration)

A completely different way to look at it would be by wavelength and actual photon penetration through the leaf tissue to be converted by the photosystems, and in this case, light sources with heavy green would offer the best penetration as once it enters the leaf it reflects around inside much more than blues or reds which are absorbed.

Its just one of those terms that could mean many things... sorry I'm high and rambling.. So far I love the discussion...

 

[Hosebomber]

Another way I have seen it referred to in a abstract was the difference between PPFD reaching the top of the canopy vs the lower canopy... which then would go along with more of the point source vs offset light source idea...

This is exactly what it is referring to. Once you do the calculations involved, penetration is the light that a plant receives below the top receptors.

I generally use the term when referring to 3 watt vis 5 watt diodes. The 5 watt diode has a higher PPFD when released from the chip. Once it drops 12 inches into the canopy (or below the top of the plant matter) it has exactly half (roughly speaking) of the photons it did 12 inches previously. Seeing that it starts out with more, half of that number is much greater than half of what a 3 watt would have. I'm horrible at explaining things.

 

[timothypaul26]

I always thought they were talking about how well a light can penetrate the canopy. In true nature, all types of weeds would grow around the canabis and would have a canopy around it. Same type of theory, all of our plants in a tent or room would create a canopy. That was always my interpretation.

 

[mdelio]

This all sounds good as Hps and Hids go,.. but LEDs have a focus point some where between the canopy and the Leds, so I think it is more important to know the focus point of the LED panel to get maximum penetration, correct me if I am wrong.

 

[Hosebomber]

LEDs in and of themselves are point source lights. It just happens that you have a panel of them giving you 96 or 300 or whatever the panel is made of as point sources.

 

[rick3066]

huh?

 

[Icemud]

The whole use of the word is still misleading I think and confusing. I've actually been finding articles that diffused light or "soft light" actually has far better canopy penetration than direct light or "hard light" and actually drives photosynthesis better, as well as even with a reduction of light intensity by 4% of diffusion medium, the increase in yield and weight was 6-10% higher than direct light because less shadowing and more even canopy penetration.

Therefore when we hear the word "penetration" as how it is used by lighting companies, I think "like a flashlight" focused light beams, but now from the information that I am finding and that diffused or soft light actually penetrates the canopy more, it seems even more misleading.

its like a laser beam would have excellent penetration by definition of "throw" but horrible canopy penetration when looking at spread over the entire canopy. As soon as the laser hit a leaf, there goes the penetration into the canopy vs a diffused or soft light source which actually allows the photons spread more evenly across the canopy...

 

[Hosebomber]

Can you link or PM me the studies please?

 

[ButADream]

Interesting.

 

[ibaba]

After reading this and some other people saying the same thing I have taken off the lenses. I have some small grow bulbs with 3 red and 2 blue leds, without lenses the color mixes much better at a closer distance to the canopy, which is another bonus .

 

[Twilight LED]

Yes ibaba, the lenses will have the function of Condensed Light, so the different color will be more separate through lens.

After reading this and some other people saying the same thing I have taken off the lenses. I have some small grow bulbs with 3 red and 2 blue leds, without lenses the color mixes much better at a closer distance to the canopy, which is another bonus .