Lens and Reflector Optics for COB

[wietefras]

you have made a circular argument here, and you don't seem to realize it. Your assumption (which is different from everyone else) is PPFD if measured in the whole grow the room, the entire footprint, but everyone here is taking about PPFD ONLY for the canopy.

No, I'm talking about the canopy also.

Or rather, it doesn't matter. The PPF determines how much light goes in and the surface area determines the average density.

It's like throwing 100 liters of water in a tub that's 100x100cm. What is the height of the water? If you push the water down (push a bucket in) on one side or pull it up (suck on a pipe) the local density (height) will change, but does the average height of the water change? No of course not. Same with how PPF gets divided over an area resulting in a average PPFD that can not change.

'So the increase in PPFD under the COB is caused by taking away light from other parts of the grow area. In the end the average PPFD over the whole grow area is still the same.'

here's your mistake. The PPFD over the whole grow area is the same because the size doesn't change, but when you take that spread and redirect it down, your by definition get more PPFDENSITY because the same amount of photons are now directed towards the canopy and not the entire grow room. And because you now have more photons in a smaller area, by definition your penetration will also increase.

That is indeed the mistake many people seem to be making.

Where do you think the extra light for the higher intensities is created from?

Reflectors don't create light. They bundle the available light into a smaller area. Outside that area the densities are now lower.

Again, PPF is like throwing a buckt of water in a confined space. You might push it down on one side, but it will go up on another side. The average depth will always be the same.

This is clearly demonstrated in the charts Robin has posted. Am i missing something here? Regardless of all this theory, real world results show an increase in yield with the use of optics, so tell me what happening here other than more photons being delivered in a more useful way to the plants.

And that is another mistake. The charts Robin has posted only show only the light that is inside a measuring grid. The COBs without optics throw much light outside that square and this is not counted. Do a proper flat plane integration and you will see that all the light is still there and averag PPFD will not have changed. Over a much larger surface than 2'x2' though.

Really, the average PPFD can not change by using a reflector (ignoring reflection losses for the moment). The density increase that you see under the COB means that you are decreasing the density somewhere else.

 

[wietefras]

Here is some more depth
...
Keep calm and grow weed and please let us know how reflectors perform for you.

I'm plenty calm I like the testing you have done, but you are missing just this single point. Try to understand what I'm saying instead of simply dismissing it.

You really cannot create light from nowhere with a reflector. So these photons have to come from somewhere else. There is no place for reflectors in the equation "average PPFD" = PPF / "surface area in m2". Local increases are posible of course, but they will result in a decrease of light intensity somewhere else.

 

[robincnn]

Again, PPF is like throwing a buckt of water in a confined space.

water follows gravity light not so much.

I appreciate your opinion. Not dismissing it either. Your theory seems correct.. But grow space is slightly more complex and many variables at play.
Have you tested a grow with any optics like reflectors or lens?

Wide angle Reflector does not create light. Optics is just a tool to shape the light distribution so that it has more photons reach your plants and less are lost in process.
Good optics just shapes the light for better penetration. Without optics that light would not have penetrated mid and lower foliage and would have stayed near top canopy.

 

[hillbill]

Reflectors or lenses are simply tools that put the limited amount of light we have into an area which will do the most good in a particular use. Lenses are even used in search lights, headlights, flashlights, warning lights, brake lights and on and on. Reflectors and lenses together even.

It also costs very little to try. Just do it!

 

[ttystikk]

The most valid test IMO.

I do appreciate all the work you have done on this. I don't expect many people to pack 14 cobs in an 8 square foot area and despite my insistence that there are good reasons to leave them off I think some types of optics are a good idea in most grow situations.

Here's why I went with lenses; long term protection plus better penetration and depth of field to do a good job on plants as close as 12" and as far away as 36". I'm running a sizeable array, which certainly helps.

 

[Rahz]

I think it's cool there are options, makes the subject more interesting. I was originally going to sell lamps without the optics and offer a couple add on options. I went with lenses because they offer protection They can always be taken off, but if they're already on there not much point.

For myself, having a total of 37 cobs over 26 square feet I still don't feel the need to upgrade. The lamps are an open frame design. I had a stretchy indica growing a while back. About 1/3 of the tops ended up growing through the frame, some of them 6-8 inches above the cobs. That's penetration

 

[wietefras]

water follows gravity light not so much.

I appreciate your opinion. Not dismissing it either. Your theory seems correct.. But grow space is slightly more complex and many variables at play.

OK, a bucket of photons then.

Still the fact that a test like this is actually rather complex is exactly my point. People are refuting irrefutable physics laws by saying reflectors will give them 20% extra light. Reflectors don't add light, so if you see a higher average PPFD with reflectors it means there is something wrong with the test. Either through measuring errors or because light is being lost.

With regards to meauring errors, if you look at the footprint of the light with a reflector attached, the circle is quite clearly delineated. So measure an inch to the left or right around the edge area and you will see a huge difference in measured PPFD. With a much higher or much lower sqft PPFD value as a result. Of course the average PPFD over that entire sqft won't change so so dramatically and so it's easy to introduce measuring errors. Not sure how you can easily fix that, but more measuring points would help. Or perhaps use a photo of the light footprint and compare that instead. That's not without it's difficulties either though (always needs the same camera settings and angle)

Also, diamond reflective material is actually a bad choice for walls. It's a retroreflective material. That design is intended to send the radiation back to the point of origin. Like a radar beacon or a road sign. Reflectance might be high, but the light is not going down to the plants so much. So having that on the walls in the test setting is going to cost the wider beam angles more light than the tighter ones.

Have you tested a grow with any optics like reflectors or lens?

Wide angle Reflector does not create light. Optics is just a tool to shape the light distribution so that it has more photons reach your plants and less are lost in process.

No I have not tested reflectors, I'm just working with basis physics laws here and from that I'd say it's clear that reflectors won't beat my reflective walls (even though they could be better). Of course there can be other benefits like being able to move the fixture up higher from the plants or that they protect the COBs.

Strictly talking about average light intensity though, all reflectors do is exchange wall losses for reflector losses. So it comes down to how well your walls reflect (or not)

If you have walls with nice direct reflections, there is no way reflectors will come even close. On the other hand, if you have very poor reflective walls then reflectors will work much better. Those are the easy cases.

Somewhere in between I would say the walls still beat the reflectors because less light will hit the wall as opposed to a reflector. Not going to repeat my poorly drawn light distribution chart here but it does show how much of the light is hitting the reflector which would never have hit the wall without a reflector present. That means the COB reflectors need to be significantly more reflective to beat reflective walls. So even with only reasonably adequate reflective walls, the walls will still beat reflectors.

[/QUOTE]Good optics just shapes the light for better penetration. Without optics that light would not have penetrated mid and lower foliage and would have stayed near top canopy.[/QUOTE]That's based on the notion that reflector leaves you with more light. Which is only the case if you have rather poorly reflective walls.

What do you think "penetration" is though? Cause it's not really a physics term. Increasing intensity would mean that further away from the light you still have enough light available for adequate growing. Adding more light is then usually called "deeper penetration". PPF does that and reflectors only if they prevent losses from lack of reflective walls.

Another definition, from green house growers, is ho easy the light slips between the leaves. If you have diffuse light it is much better at moving in between the leaves (also of course when there are less leaves). Also having some light come in at shallower angles also makes it easier for the light to move between the leaves. Lastly, spreading the light out evenly also helps with that.

Adding a reflector to tighten the beam makes the light less diffuse and therefore actually hinders that type of penetration. More of the light will then just hit the top canopy and either be absorbed or reflected to the ceiling and gone. If it slips between the leaves, even if the leaves don't absorb it and reflect, the light will be taken up by another part of the plant. Although I doubt that diffusion will have a measurable effect in a hobby grow. I have seen professional test reports and they only saw a few percent more yield with more diffuse light. That's well within variance in yields between grows for the type of grows that we do.

 

[badtorro]

OK, a bucket of photons then.

Still the fact that a test like this is actually rather complex is exactly my point. People are refuting irrefutable physics laws by saying reflectors will give them 20% extra light. Reflectors don't add light, so if you see a higher average PPFD with reflectors it means there is something wrong with the test. Either through measuring errors or because light is being lost.

With regards to meauring errors, if you look at the footprint of the light with a reflector attached, the circle is quite clearly delineated. So measure an inch to the left or right around the edge area and you will see a huge difference in measured PPFD. With a much higher or much lower sqft PPFD value as a result. Of course the average PPFD over that entire sqft won't change so so dramatically and so it's easy to introduce measuring errors. Not sure how you can easily fix that, but more measuring points would help. Or perhaps use a photo of the light footprint and compare that instead. That's not without it's difficulties either though (always needs the same camera settings and angle)

Also, diamond reflective material is actually a bad choice for walls. It's a retroreflective material. That design is intended to send the radiation back to the point of origin. Like a radar beacon or a road sign. Reflectance might be high, but the light is not going down to the plants so much. So having that on the walls in the test setting is going to cost the wider beam angles more light than the tighter ones.


No I have not tested reflectors, I'm just working with basis physics laws here and from that I'd say it's clear that reflectors won't beat my reflective walls (even though they could be better). Of course there can be other benefits like being able to move the fixture up higher from the plants or that they protect the COBs.

Strictly talking about average light intensity though, all reflectors do is exchange wall losses for reflector losses. So it comes down to how well your walls reflect (or not)

If you have walls with nice direct reflections, there is no way reflectors will come even close. On the other hand, if you have very poor reflective walls then reflectors will work much better. Those are the easy cases.

Somewhere in between I would say the walls still beat the reflectors because less light will hit the wall as opposed to a reflector. Not going to repeat my poorly drawn light distribution chart here but it does show how much of the light is hitting the reflector which would never have hit the wall without a reflector present. That means the COB reflectors need to be significantly more reflective to beat reflective walls. So even with only reasonably adequate reflective walls, the walls will still beat reflectors.

All indoor growers use reflectors in addition to reflecting walls for many many years.
The experience clearly says to use reflectors. That's the case with CFLs, same story with HIDs etc.
Do you think something has changed since instroduction of leds or cobs specifically?

It's always better to have reflectors then not, because it reduces the amount of times a light wave has to bounce before it reaches a canopy.
Same story with leds. Obviously a lens or reflector doesnt produce new lights, merely reduces the amount of bounces before penetrating weed.

sorry if I'm not making myself clear, I'm stoned

 

[ttystikk]

All indoor growers use reflectors in addition to reflecting walls for many many years.
The experience clearly says to use reflectors. That's the case with CFLs, same story with HIDs etc.
Do you think something has changed since instroduction of leds or cobs specifically?

It's always better to have reflectors then not, because it reduces the amount of times a light wave has to bounce before it reaches a canopy.
Same story with leds. Obviously a lens or reflector doesnt produce new lights, merely reduces the amount of bounces before penetrating weed.

sorry if I'm not making myself clear, I'm stoned

You are incorrect in your assumption that all indoor growers use reflectors. I do not and haven't for some time now.

 

[wietefras]

All indoor growers use reflectors in addition to reflecting walls for many many years.
The experience clearly says to use reflectors. That's the case with CFLs, same story with HIDs etc.
Do you think something has changed since instroduction of leds or cobs specifically?

Look at how a CFL or HPS bulb spread their light 360 degrees around. If you hang an HPS bulb horizontally, half the light goes up towards the ceiling. To get some of that light down onto the plants you will most certainly need a reflector (or lose a lot of light).

A COB already sends all the light it produces downwards. It does not need a reflector for that.

So yeah, huge difference with COBs.

 

[ttystikk]

Look at how a CFL or HPS bulb spread their light 360 degrees around. If you hang an HPS bulb horizontally, half the light goes up towards the ceiling. To get some of that light down onto the plants you will most certainly need a reflector (or lose a lot of light).

A COB already sends all the light it produces downwards. It does not need a reflector for that.

So yeah, huge difference with COBs.

Who said anything about 'down'?

 

[littlejacob]

Bonjour
Why not some "half" reflector on the side...just to reflect the part of the cob who is next to the walls...lol!
CU

 

[The Dawg]

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[ttystikk]

A Bucket Of Photons Is Better That A Barrel Of Small Penis's Just Saying

Now That I Have Laid That Piece Of Wisdom At Your Feet Here's Another Piece Of Important Information

https://www.verical.com/pd/ledil-led-accessories-F13838-ANGELINA-XW-793993?utm_source=FindChips&utm_medium=BNL1Feed&utm_campaign=FeedLowestPrice

You may catch more flies with honey than vinegar, but a turd works better than both of them!

Just chucking more wisdom at the fans out there, so to speak...

 

[The Dawg]

You may catch more flies with honey than vinegar, but a turd works better than both of them!

Just chucking more wisdom at the fans out there, so to speak...

When You Chuck Your Wisdom At The Fan So To Speak Make Sure To Duck Quack Quack

 

[ttystikk]

When You Chuck Your Wisdom At The Fan So To Speak Make Sure To Duck Quack Quack

I stand behind my turd chucking.

 

[The Dawg]

I stand behind my turd chucking.

Lmao Well That Sounds Like A Shitty Job To Me Lmao

 

[Fastslappy]

what u guys burnin right now ?

 

[littlejacob]

Witches!

 

[ttystikk]

Witches!

Super Lemon Haze. Very tasty, keeps coming.