# Penetration nonsense.

Discussion in 'Lighting' started by Swami, Jul 7, 2011.

1. #1
This concept is pure silliness and yet is bandied about as if it has merit. If there were such a thing, it would have a clear definition and a way to measure such, but it doesn't.

Let's take a single photon. It can travel the length of the universe unless obstructed, so it can probably travel 5 feet unless obstructed. The sun is the most intense light in the solar system, yet cannot make it to the floor of a thick rainforest or jungle.

So it is not merely distance nor intensity. Then what is penetration? Who knows? If it is merely lighting up lower leaves then a couple of well-placed low watt cfls must have awesome penetration.

If it is merely lighting up the lower leaves then two widely-spaced 250w HPS have better penetration than a single 1000w HPS.

Unless someone has a solid and measurable explanation, this 'concept' should be stricken from the cannabis lighting lexicon.

2. #2
Its measured in bud size. Grow with purely CFL's 250w only lighting from the top and tell me how big your bottom buds are. Then do the same grow with a 250hps and tell me how big your bottom buds are. All the proof you need.

3. #3
Yea but how is this consider the effect of penetration? All light gets blocked even the sun which is of course greater then hps lights. I have to agree there has to be a better way to explain it then say "Penetration".

4. #4
Last edited by a moderator: Jul 9, 2011

First off, you're comparing how light travels in a vacuum to how it travels through our atmosphere. Light can travel much, much further through space than it can through the air on our planet.

Secondly and much more importantly, you're not considering the size of the light-emitting substance. Some people will understand better after drawing what I'm saying to imagine. Imagine two separate light sources. Instead of the normal field of light, imagine each source two-dimensionally as a point with sixty rays equidistant from each other, like a clock with each of sixty hands pointing at a different minute. Each hand represents a ray of light.

Now imagine a two-dimensional plant centered under the two light sources. The closer you imagine the plant to the light sources, the more of those 120 rays will run into it. The further away you imagine the plant, the fewer rays will run into it. Also, the further apart the two light sources are, the fewer of those 120 rays hit the plant. This is exactly why distance from the lamp is so significant to light intensity. It's also why the light from many fluorescents doesn't reach very far; the light is emitted from a much larger area than with an HID, for example, and so has much more of this effect.

The light emitted by a smaller source will reach further than the same lumen output emitted over a larger area.

5. #5
the light field created by any source grows exponentially as you get further away from the source, so the density ,if you will, of the light diminishes exponentially the further you get from the source. The photons will hit something, but they are all traveling away from each other as they travel from the light bulb, so each square inch gets less photons hitting it the further you are from the light. Obstructions only make it worse.

6. #6
You brought up yet another oft-repeated misunderstanding. The inverse square law applies to omnidirectional light sources: CFL, HID, fluoro, incandescent. The math and the diminishing effect is quite different for LEDs; the amount being based on the beam angle.

7. #7

No, it is not.

The HPS puts out more lumens or has a much greater photonic output than the CFL. This much can be determined.

There is no measurement for penetration. It is some made-up, nebulous term that keeps getting repeated by people who do not understand.

8. #9
I think it's great that you can link articles. Did you have a point?

9. #10
You said it was nonsense. I gave you all the information in those two links to prove to you it isn't. Feel free to read them and educate yourself.

10. #11
I can see how you think marine measurements are relevant and therein lies the problem with your inability to condense the articles into a concise statement that might be called on.

Can you tell me how many penetrons your lamp puts out or what its penetration factor is? Of course not!

Light sources have a limited number of parameters: luminous flux, radiant flux, spectra, chromaticity, lumen maintenance, and spatial distribution are among the most relevant. There is not a single parameter that is a measurement of penetration.

11. #12
Penetration nonsense is just that NONSENSE!!!

A photon that have a wave of 660nm have certain amount of energy no more no less!! It's a energy pocket which energy is solely determined by the wavelength since the speed of light is the same for all electromagnetic waves!!

If two photons with same wave length interfere then it's two photons hitting the same spot twice, rather then one "combined photon" hitting twice as hard!

A 660nm wave (red, chloro A) has the same penetration level regardless if it's being emitted by an HPS bulb or a candle light!! It's just that HPS emits many more photons then a candle light.

12. #13
The above it's physics, tho. There could be some biological processes that prevent photosynthesis unless the light intensity is strong enough!

Perhaps plant is thinking: ahh man, it's just to little light around, I better sleep and save energy until more arrives, I dunno, could be..

13. #14
Just because we haven't invented a standard measurement system for it, doesn't mean we cannot observe the effects of penetration.

But in essence we can increase 'penetration' by adding side lighting, because the only 'penetration' is that of the light through the canopy. And likewise, if you have a canopy that lets through a slit of light that is 1" long by 1/4" wide and that falls on a single leaf that is then absorbing that light. Well if you have a source of light that fits more photons in that same area it could essentially be said you are getting MORE penetration because there is a higher level of energy available at a level in the canopy further towards ground level.

I'm not sure why it's a big deal, but I bet we could come together as a community and scientifically decide on a way to measure and define penetration. That's pretty much how scientists and such decide upon terminology so that they can re-create the same lab conditions across several labs and confirm results.

Penetration is an ambiguous term, but instead of getting rid of it altogether maybe we can just define it instead?

Haha who knows, I smoked halfway through typing this and forgot about it. Peace

14. #15
OMG. this is such a simple concept. The overhead light is not able to PENETRATE through the dense canopy to provide the same intensity of light to the lower foliage as it naturally would on the upper foliage. Whether your overhead source is CFLs, HPS, or the Sun...the light is going to get blocked and the lower nodes will received a fraction of the lumens that the uppers will.

This concept is not novel or exlusive to growing cannabis either. I worked in TV/film/video lighting for 5+ years, and the same concepts apply. ALSO, the intensity of a light "dies off" the further you get away from the source, relative to the base intensity of the light in the first place.

15. #16
"The overhead light is not able to PENETRATE through the dense canopy to provide the same intensity of light to the lower foliage as it naturally would on the upper foliage."

Nowhere did I say the word could not be used in a meaningful way in sentence. What I said is that one light may be said to have greater photon flux density than another, but penetration is the result of how your entire growing setup is laid out and NOT a property of the light.

16. #17
At least one reader understands.

17. #18
Penetration is BS. Light is emitted at different angles from a bulb, therefore as you increase distance the total number of photons hitting that point is exponentially less.

HID does not "penetrate the canopy better" than a CFL. It's just that CFLs have less intensity as there is more surface area that the light is coming out of. This just means that their performance is even more dependent on the reflector than HID lights...and of course they also run cooler therefore you can put the canopy closer to it.

18. #19
Last edited by a moderator: Jul 10, 2011

Like a few others, you're still not considering the number of photons coming into contact with the plant. Their wavelength is irrelevant to this concept. If every photon emitted by a light source were travelling in the exact same direction, then distance & penetration (at least in a vacuum & excluding gravitational forces that aren't relevant at this scale) wouldn't be a factor- every photon would eventually contact the object it is travelling toward regardless of distance.

However, the lights used for growing do not emit every photon in the same direction. Because grow lights emit photons in all directions, the closer an object is to the light, the more of this spread of photons will collide with it.

19. #20
This is really silly. Penetration simply means how much light reaches to whichever part of the plant you are concerned with. It can be measured, with a light meter. If the light has a straight unobstructed path then the spot in question is getting full penetration. If the direct line of sight from the light source is blocked then that area is shaded and gets some reflected light. The amount of reflected light depends on a lot of things, but among them are the intensity of that light and the distance it has to travel. CFLs have low intensity to begin with, so their reflected light becomes too low to "penetrate", simply meaning too low for the plant to meaningfully use.

More light to more of the plant is better, I don't know any MJ grower who could argue with that. So why is this an issue?