Lens and Reflector Optics for COB

What Optics do you use in your DIY Lamp

  • No Optics

    Votes: 132 45.4%

  • Glass Lens

    Votes: 58 19.9%

  • Reflector

    Votes: 118 40.5%

  • Silicone Lens

    Votes: 23 7.9%

  • Other

    Votes: 6 2.1%
  • Total voters
    291
wietefras

wietefras

Well-Known Member
SaltyNuts said:
for canna it often becomes important to focus the light toward the canopy, instead of it radiating in shallow angles to the canopy, especially if you have more cobs running softly.
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That's only a hypothesis and one that makes no sense at all.

Put your head 60cm or 2 foot above the canopy and look straight down towards the canopy. Can you see through?Hardly huh? Now move your head lower to 30cm or 1 foot and turn your head to a more shallow angle. All of a sudden you can peek between the leaves.

Now in which of those two examples would you get more light penetration?

Apart from the obvious fact that the extra reflector losses and almost double the wall losses, due to increased height, means you get 20% less light on the plants with reflector encumbered COBs compared to bare COBs.
 
SaltyNuts

SaltyNuts

Well-Known Member
The focus was lenses in particular the Stella HB, not reflectors. Nowhere do I advocate reflectors. I made a point that a doubling of the number of cobs, respectively, while using the same total wattage, in this case at comparable efficiency, would create approximate equal PPF, but unequal PPFD. That due to doubled lateral diffusion (double the emitter area), which may or may not be desirable depending on how you feel about penetration. But I can't speak for you. The concern here is the lower-powered cobs outputting a sufficient beam of light. Hence the lenses. The lenses focus the light in beam pattern that has more stable PPFD over these short distances, versus the light distribution pattern from bare emitters broadcasting at 120 degrees or greater, whence there is more variance in the intensity depending on how far from the source, as opposed to the beam. I pointed out that bare emitters are fine depending on your growing conditions. Plenty of people can attest to that. As long as the plants are receiving the light in adequate density it's all good however you go about it. I like the idea of the highly distributed point sources that can get close but have a focused PPFD that can "penetrate" in a downward direction in case of 2' -3' canopy. So that's what I was plotting out with the thirty-two 1212 array at 700mA and lenses over a 4x4. Ultimately though, that build is a wash, as the new cobs are coming out.
 
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SaltyNuts

SaltyNuts

Well-Known Member
you do have a point though that I made an assertion that is really only a hypothesis. Can I be stoned once in a while. Jeezus.

"for canna it often becomes important to focus the light toward the canopy, instead of it radiating in shallow angles to the canopy, especially if you have more cobs running softly."

I love it, I sound like one of those wonks in a trade mag. Gimme a break. Christ.
 
wietefras

wietefras

Well-Known Member
Most of it applies to reflectors too obviously. Only difference really is that you can clean lenses. Other than that there are still losses in the optics and you need to hang the lights higher to get proper uniformity which increase wall losses again. In the end you lose a lot more light using optics.

Your points about "stable ppfd" due to direct light make no sense either. Using more COBs to produce the same amount of light in over the same space gives you exactly the same PPFD as well.

Besides, diffuse lighting is better for the plants than direct light. Exactly because, as I explained briefly already, that direct light gives you less light penetration.

Diffusion also creates better uniformity. Imaging putting distinct circles (100% direct light) on a surface. it's going to be a uniformity mess. Some places will get no light at all while other spots will get multiple times the base light (if you have multiple emitters). The more diffusion you add the better the lights gets spread out and thus better uniformity. That also means you can hang bare COBs a little closer (cutting wall losses) than based on beam angle differences alone.
 
PhotonFUD

PhotonFUD

Well-Known Member
You both are right. It depends on environment. Totally. The two of you are debating the equivalent of whether purple kool aid is better than green.

And keep in mind that I am always promoting more cobs under driven as the solution to everything.
 
SaltyNuts

SaltyNuts

Well-Known Member
This thread is about optics so the discussion is appropriate. I don't have a bone to pick. I'm all about the diffuse source, that is a major advantages of LED over HID. Ask the Dutch guys who've been using 400W HPS for the last 30 years. Use logic and suspend ego. That's why I was talking about using 32 cobs at 700mA to cover a 4x4. The closer the emitters are to the canopy the less light is scattered to the walls and wasted in reflection, whether you are using bare emitters or optics that holds true. The topic is focusing the light versus allowing bare emitters to scatter it, and how that has an effect on this thing people call "penetration". Both have their application. I said that already. My assertion is that focusing the photons reduces potential losses from scattering, in the case of a certain canopy depth. The "stable PPFD" I referred to is a made up term to describe the image of the cone of light traveling in a directional beam pattern, versus a broad emission from the bare emitter. The point is that the direction the photons are traveling is relevant to this concept of "penetration". Go back and read Robins post, that's really what I wanted people to do, not listen to me rant.

My hypothesis is (say it fast) about these particular lenses, the Stella HB - which Robin covered in depth earlier comparing bare emitters, reflectors, and a range of lenses. He provided graphic data with PAR values he recorded using a range of fixtures. I looked at that and it inspired my post. Full props to him. I suggest anyone go back and review it. Look at his graphs and examine the PAR data taken at various mounting heights.

If you present logic and data and humor I am there and will be back for more. So the question is would the Stella HB lenses help make the 700mA-driven cobs more efficacious in terms of "penetration" by focusing the light, while still being safely mounted close to the canopy? No way to know except to try it. But the PAR graphs posted by Robin show substantial increase in PPFD in the 1'x1' area when using the Stella HB lens. And he comments on that lens in particular, that it may be ideal for low-power cobs given the way it focuses and directs the light off the les. So I'm going off his data with a "what if" scenario.

By "stable" I mean that the beam diffuses less over distance so you get more consistent PPFD at a greater range of distances from the single emitter in a given area, here 1'x1'. If the emitter broadcasts at 180 degrees the PPFD drops off quicker in a given area as you increase distance from the light emitting surface. Not counting the overlap from other emitters. That's another thing, but if it makes lenses unnecessary that's great. I haven't seen that data please link it.

Reflectors work similarly to lenses, of course. Either one is going to have losses even when brand-new and spotless. And both get dirty and both age. There are downsides to every choice. But this thread is about optics. And I'm talking about a particular lens.

To argue in favor of optics when using lots of soft emitters, just observe that the best LED fixtures on the market using single diodes are distinguished in large part by the quality of their optics. I stand by my point that the more you distribute point sources of light, with lower output per source, the more it may be an issue of needing to focus the light to overcome the tendency for the emitters to broadcast light 180 degrees. And that depends on your application. And I'm not making hard claims here or stumping for any brand, this is off my head, but I try to be logical and I think it makes sense if you take the time to think about it.
 
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SaltyNuts

SaltyNuts

Well-Known Member
wietefras said:
Your points about "stable ppfd" due to direct light make no sense either. Using more COBs to produce the same amount of light in over the same space gives you exactly the same PPFD as well.
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I think you are incorrect. Equal PPF but unequal PPFD. But it depends on distance from emitters, and beam angle.
 
SaltyNuts

SaltyNuts

Well-Known Member
ttystikk said:
Glass lenses don't degrade. They protect the chips from environmental damage like overspray. They focus light downward onto the canopy. For these three reasons, I still think lenses were the right choice for my array made of 4 chip modules.
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I'm all about the lenses, it's all over riu. Bare emitters are for effeminate dudes wearing tight shorts.
 
The Dawg

The Dawg

Well-Known Member
ttystikk said:
Glass lenses don't degrade. They protect the chips from environmental damage like overspray. They focus light downward onto the canopy. For these three reasons, I still think lenses were the right choice for my array made of 4 chip modules.
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Agreed Plus They Protect The Cob When The Boyz Take's A Shower :P
 
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