How to Plot PPF Chart with Quantum Sensors for LED light comparison

I am also surprised by the good result for the lens, but I think it is rather for the bad performance (translucence) of the reflector. Would love to see cheapo reflector alternatives in the same setting.

This candle bowl, painted white.
This french fries bowl, or similar.
This 280 aluminium food bowl, in different bends.
The top "coke part" of a 2l coke bottle, painted white.
And maybe a simple, bent, hammer finished sheet.
Or use what you have. I remember somebody even used tuna cans

Khatod don't have them in stock. I will put their tests mid next month.

I posted a chart of Generic ufo here. However that was from some time back and was not taken in the same setup as all other tests.
Here is chart of Generic UFO and Vero 29 (No Optics) in the same test setup.
Some(at 420magazine.com) might argue about the magical powers of Red/Blue wavelength. Vero 29 gives of almost 3 times the PPF.

Here are all King Bright lens


Left to Right
100mm 80 Degree, 77mm 90 Degree and 77mm 120 Degree

FN14074_STELLA-HB
Looks very cool. Smells very weird, must be the flexible Silicone. Inner diameter is around 33mm so not sure how it will fit on a CXB ideal holder. May be the lens itself will put pressure down to secure COB. Not sure. No installation detail on website.
VERO29 69 deg HighBay 94 %

Left - King bright 77mm 90 degree
Right - Stella 70 degree $22.28

robincnn said:

FN14074_STELLA-HB
Looks very cool. Smells very wield, must be the flexible Silicone. Inner diameter is around 33mm so not sure how it will fit on a CXB ideal holder. May be the lens itself will put pressure down to secure COB. Not sure. No installation detail on website.
VERO29 69 deg HighBay 94 %

Left - King bright 77mm 90 degree
Right - Stella 70 degree $22.28

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is a 2 foot square enough to show the differences ?

is a 2 foot square enough to show the differences ?

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Its a valid question. To truly test the performance of one single silicon lens vs a glass lens, a 4 square foot area is probably not a large enough test area. But then you have to ask, who here is running 1 COB per 4 sqft? Most people are running a minimum of 2 or 3 cobs over 4 sqft. I think the question that robin's test answers is: should I spend $22 on a Si lens when a $5 glass lens performs better in the high density COB/sqft arrays that we are building around here. Thats my take on it anyways.

Growmau5 said:

Its a valid question. To truly test the performance of one single silicon lens vs a glass lens, a 4 square foot area is probably not a large enough test area. But then you have to ask, who here is running 1 COB per 4 sqft? Most people are running a minimum of 2 or 3 cobs over 4 sqft. I think the question that robin's test answers is: should I spend $22 on a Si lens when a $5 glass lens performs better in the high density COB/sqft arrays that we are building around here. Thats my take on it anyways.

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its not a matter of running a single cob in 4 sqft, its to understand how wide the spread is.
if I can get a full 4x2 even spread from a single row of cobs, that's easier than trying to put a row of cobs every foot, since that means a heatsink module every foot.

oh btw I picked up some samples from verical while still not dirt cheap, a lot better than 22+ each.
https://octopart.com/search?q=FN14074_STELLA-HB

I don't see myself installing lenses on my lamps any time soon. I have a 14 and 23 cob lamp and light spread at 8-10 inches is excellent on both. The default Lambertian curve is perfect for blending output. There is still some side light, but as or more important than my arrays are the reflective walls in my spaces. Assuming the walls are 80% reflective the percentage of light getting to the canopy is close to 100% without optics.

I don't think it hurts to use them, but it's kinda like Coke or Pepsi in some situations.

I think the lenses are "good" for commercial units that want IP67 rating, but I guess we should just switch off the circulation fan or lift the lights before we spray. I really don't see the point of sacrificing 10-20% of the total light output to redirect those 5ish% that would have gone lost without the lens. That is even more important for expensive setups, as (e.g. for 5xVero18 vs 4x Vero29 at 700mA) you may easily pay more than double the price to get those 3,2 percentage points higher efficiency. For ≥50W luminaires I also would not want to tighten the already quite intense beam any further, as I recall the plants like diffuse light. And, finally, thinking of good old HPS: We didn't care too much about reflector/wall losses before, did we? I think the directionality of SSL itself is good enough for homebrew and can be amended easily with some more or less sophisticated makeshift reflectors.

what Multimeter do you use with the Sensor?

And, finally, thinking of good old HPS: We didn't care too much about reflector/wall losses before, did we?

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I think the mindset of the advanced grower has changed dramatically. there are more suppliers/competitors than ever before, increasing quality, quantity and efficiency is paramount. A 3-5% increase in any of these areas effects the bottom line...

I just want to use every part of the buffalo, leaving none to waste.

I agree there's always room for improvement. But some features turn out to be bugs.

guod said:

what Multimeter do you use with the Sensor?

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MS8260A
I use this multimeter. I get mV and multiply by 5

SQ-120: Electric Calibration Quantum Sensor
Sensitivity 0.2 mV per µmol m-2 s-1
Calibration Factor 5.0 µmol m-2 s-1 per mV (reciprocal of sensitivity)

I agree the 2x2 may not be enough to show differences. Looking at the plot you get get an idea of light outside the 2x2.
There are 4 PPF data points from the center. 6, 8.49, 12, 16.97 inches.It is possible to estimate the light for 3x3
If cobs are close together in a 3x3 or bigger then best to not use any lens or reflector to ensure max spread. I agree if blending different spectrum best to not use any lens or reflector

These plots do not tell the whole story specially if you have reflective walls. Saw some grows here with 1 or more sides non reflective and lens/reflector can certainly help there.
The lens or reflector improve intensity even with reflective walls. Although only by 5%-10% (Will redo this test in Gorilla 2x2.5 soon and report).
The light that hits reflective walls. Not sure how much gets reflected down towards plants and not up.

These plots give some idea about the mounting height and cob distances. Vero 29 at 2.1 amps almost 10000 lumens. 3590 cob close to 8000 lumens at 1.4A so just reduce the values by 20%
If you can put 2 plots next to each other, the cob to cob distance will be 24 inches. You can overlap plots and estimate intensity for cob-cob distances like 18 or 12 inches.
Some idea about prices too. Like lens can be cheaper and offer similar spread to ledil .
Gives an idea how close can the cob get. may be close with no optics but not as close with a 90 degree lens.

Even if you have reflective walls or love the lambertian curve. Some people had concerns with foliar spray getting to cob les. So if anyone planning to cover the cob lens, it is good to know the impact on photon distribution with lens/reflector. Some people would like more penetration and lens/reflector can certainly help with that.

Most commercial multi LED panels other than Chinese panels use lens. Same might not be applicable for cobs. Area 51 corrects only 10% of the beam if i remember their post right. Bad optics or narrow beam can certainly be bad. Benefits of good optics are debatable in grow room with reflective walls. Would be nice to see a side by side grow.

Why test optics. May be they have a secret sauce to improve coverage . Who knows may be bat wing curve can offer more even coverage than the Cob's lambertian curve.
94% efficient drivers and 60% + efficient cobs. May be cheep optics options can help a little with efficiency.

Saw some good articles when I googled diffused lights benefits for greenhouses. 2000PPF of sun seems too high and diffusing it seems like a good idea. However in a space with 600PPF, a PPF gain with lens or reflector may yield more than the diffusion gain without lens or reflector. 80+ degree spread of a lens/reflector should not hurt the diffusion too much.

Some 90,120 degree non center focused lens and reflectors may still provide enough diffused light but good to stay away from anything with a beam narrower than 90 degree.

I am just throwing some plots to confuse you all. If anyone can make any sense... let me know

edit: Saw some PAR meter rentals today. $20/week
http://aquariaguru.com/product/rent-par-meter-mq-200/
https://reefledlights.com/shop/par-meter-rental/

robincnn said:

I am just throwing some plots to confuse you all. If anyone can make any sense... let me know

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lots of good ramblings in your post. food for thought, thanks for the hard work it is helpful. even in the 2x2 I am getting an idea of how the wider spread lenses behave.

Great work here!!! Keep it up! Props!

Came across a Chrome extension called 'Ray Optics Simulation'
https://chrome.google.com/webstore/detail/ray-optics-simulation/egamlemiidmmmcccadndbjjihkcfiobh

Good to test some basics of optics. It has a scale so we can draw any optics to scale and test it out. You can draw a lens and see how the COB distance impacts the beam. Little hard to make a lambertian light source but still gives a good idea.


I wondered why LEDIL reflector has some steps and not even inside the reflector.
An even reflector can create hotspots so the steps might help with diffusion to avoid hotspots.


The reflections from reflector just scatter (diffuse).
Lens tighten the beam more evenly than reflectors. But then again the diffusion of reflectors has its own advantages.


No Optics


With a small lens it important to make sure COB aligns in the middle. Bigger lens can be more forgiving.

Here is an example of curved reflector i came up with while trying to make a reflector that will direct so extra light to sides so that sides have similar intensity as center.


Some other pics attached. One of the attachments is the 'Converging Meniscus positive' the kind used for COB. Its like plano convex but flat side in curved inside to have some clearance for cob.

Should have Khatod lens results with vero 29 by next weekend.

That is an incredible tool you found there Robin. I'm learning alot from this thread, keep up the great work.

....im still waiting for my Khatod samples from their rep. He's got my fedex acct# and everything and its been 3 weeks. Did you get yours right away>?

Growmau5 said:

im still waiting for my Khatod samples from their rep. He's got my fedex acct# and everything and its been 3 weeks. Did you get yours right away>?

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They did not have it in stock so took 3-4 weeks. I gave them my fedex account number and they said they will ship next week.

Here is my what I have tested so far

Jerry on the left top. ledil below that, khatod below that
Right top some other 44mm, 77mm, 100mm lens.

Is Khatod any good for grow rooms?
The ledil silicone stella was a little sticky type silicone. Dust gets stuck easily on its surface.
Italian Khatod is very smooth finish and looks great. Some quality silicone.



Kathud 90

Kathud 120

Here was the results with a Vero 29 3000K 2.23 Amp


I was really surprised by how even the coverage was with Khatod 120. But the spread was so much i had to put additional marker for 150 values(32-36 inches was diameter for 150 values).
But the spread so so much that it is an issue. If the COB was powerful then it might be a good idea but then cob already at 90 watts. COB will have to come too close to canopy.
Would have worked perfect if it were a little narrower.

Khatod 90. I am pretty sure i mounted it correctly. Not sure why the coverage was not as even. Looks even narrower than Stella 70 degree.
Might consider retesting this one but so far the coverage was too narrow.

Khatod and Ledil Stella is not as forgiving if not alignment properly. I did not have use Khatod special COB holders but it would have helped with the center alignment. I am not sure but availability and price could also be an issue for DIY.
So far looks like for DIY ledil reflector is best for open cob. If want to cover cob the 100mm lens is good. With reflector no worry about alignment. With 100 mm lens it is more forgiving for DIY too.