I'm trying to understand the light penetration issue with LED lights versus traditional HID lights. Is the idea that LED lights shoot direct beams that can be controlled and HID lights shoot scattered beams like a shotgun? The direct beams from the LEDs hit the top layer of the canopy and are then rebuffed and can't reach the lower levels. The scattered beams from the HIDs bounce off everything and more of the beams reach the lower levels of the plant. Am I on the right track here? I've attached an image that I created to better explain what I'm talking about here.
most of the LED fixtures that are sold use wide angle lenses. if you have properly setup your grow space, by either painting the walls, mylar, panda film, etc. you are still going to get the light refracting off of the walls thus increasing penetration to the lower growth... i have seen countless LED grows on this site and others, going from the pictures i have seen there is very little difference in plant growth in LED vs HID, except in flowering where hps wins hands down.
@swami, please expound. I've enjoyed reading some of your other posts and would be grateful if you explained why penetration is meaningless. In fact, it was your post that got me to ask this question. You said, " @jimmyjackson. From the sex books I have read, deeper penetration equaling more pleasure is actually a myth. @Samiel, great point about the walls still reflecting with LEDs. Why is it that HPS is so much better at flowering than LEDs? I'll look into it myself, but I'd appreciate any thoughts you have to share as well. Thanks!
It is meaningless when applied to a lamp, such as "HPS has better penetration than MH". For a given wattage and similar ballasts, HPS has greater intensity or luminous output, but nowhere in any spec sheet will you ever see a reference to penetration because there is no such thing. Penetration, as is improperly used, generally means how much light is hitting your lower leaves. As the sun is the brighetst object in the solar system and can easily have its light blocked to lower leaves, then penetration is NOT a function of the intensity. If I put a 13W CFL next to my lower leaves then suddenly a 13W CFL has awesome penentration? No, not really. So what is it? It is a function of your entire setup: the type and number of plants and thickness of your canopy and number of lights and their arrangement and distance and the type and placement of reflectors and the beam angle of your lights, etc. Even taking these things into consideration, there still is no metric for the penetration of a system. Does your system have 5 penetration units or 70% penetration? Sorry, it does not compute. The ONLY useful metric in this regard is to place a quantum light meter at the bottom of your canopy which will measure the photosynthetically active radiation (PAR) from 400 to 700 nm.
the reason hps is better for flowering has to do with the spectrum used by the plant during this time. the spectrum of light that a hps lamp throws off is closer to the actual color of the sun in the fall, making the buds denser, fuller, and stickier. like i stated in my previous post, this is simply going off of the information i have available to me, as i use flouro tubes and cfls personally. i have looked into LED lighting, but for the time being it is something that i personally cannot financially dabble in.
Yet more misinformation. Solar spectra change from season to season is non-existent in space and minimal after atmospheric filtering. HPS flowers better because of its greater luminous flux. It does not even come close to matching the solar spectrum.
I did contribute. Knowing that PAR isn't very useful, is good information to know for all growers. Your welcome.
Then you have a reading comprehension disorder. My statement was factual. Your response about it not being 'that useful' is not only totally vague, but had nothing to do with what I wrote. Good job!
i have to disagree with this statement, during the spring, when the earth is closer to the sun on its elipitcal orbit we do get more of the blue end of the spectrum. in the fall when we are further away from the sun the visible spectrum changes into the infared/red side... come on dude, this is frigging middle school science class right there..
It is vague because I don't feel like getting into the subject in depth. Not at this time at least. I will probably make a thread about how useless PAR is at some point, because far too many people see it as the end all be all of spectrum, but I'm lazy and haven't got around to it yet.
You don't need a source. It's just common sense. Take 2 light sources. Both are 100% PAR and both emit the same radiant flux. Light source A has all of it's radiation in the green spectrum - This is still 100% PAR because green lies within the PAR spectrum. Light source B has all of it's radiation in the red and blue spectra - Again this is 100% PAR radiation just like the light source A. Both of these light sources will measure identical in PAR watts, but light source B will grow plants FAR better than light source A because plants use very little green for photosynthesis. Basically the reason that PAR is bad is because it treats all spectra within it's range equally, whereas plants do not even come close to using all spectra in that range equally. There is big difference between photosynthetic ACTIVE radiation and photosynthetic USABLE radiation. That is why PUR is far better than PAR.
Light Quality – The spectrum of light available to plants changes throughout the year, too. When the sun is high in the sky, more of the blue part of the spectrum helps plants produce lush foliage to maximize photosynthesis and growth. As summer ends and the sun is lower in the sky, the light shifts to the red end of the spectrum, triggering maturity and seed and fruit production. One of the easiest things for the hydroponic and indoor gardener to change is the spectrum of lighting being used. Switching HID lighting from Metal Halide to High Pressure Sodium bulbs can easily simulate the change of light spectrum as the seasons change. need i go on?
You certainly confirmed my suspicion of a severe reading disorder. Your post had nothing to do with seasonal spectral change, now did it?
No you do not need to go on, you need to give a source for a significant seasonal spectral shift as I requested.
Oh I thought you quoted me asking for source, not samiel. Either way you are wrong about PAR and that's what I'm discussing. Bye.