Lighting LED lenses?

[nhdtjq]

Greetings all! I have questions about light lensing.

Finally im buying a proper LED fixture, a 220W draw panel from a local company with a mix of excellent (epistar, cree, osram) diodes and a machined aluminium frame. How nice to have a manufacturer you can actually visit on short notice!

This is the device:



They are offering lenses for this panel and ive got myself the 60 degree ones because this fixture is going to live in a 40x40cm space:



So here are my questions:

1. The tiny tent im using, does it actually need the light focused? Would the mylar not provide a sufficient ambient dispersal, when the fixture is 385x310x80mm?

2. Would having the lenses on decrease the lifetime of the diodes? I assume they would get hot as they are already lensed and would further lose contact with the airflow... maybe its to be expected, cant be avoided with 5W leds?

3. Does a second lens have a serious effect on efficiency?

4. Could i only apply some of the lenses, perhaps in the middle somewhere, to further tweak the focus across my space?

Theyre only $7 so i got them because of this:



In my case that would be massive direct light everywhere in a hypothetical scrog...

 

[nhdtjq]

Bump, but also another question for when someone eventually finds this thread - if i was to use a mix of lenses (60 and 90 degree) to efficiently cover a square area with my rectangular light, how would i best position them?

 

[namvet25]

60 degree lens are pretty narrow and they will consentrate the light in a narrow beam but will limit your footprint. You might want to use some 90 degree lens around the outer two rows of diodes to widen the coverage a little.Lenses should have little effect on diode life.Alot of lights have multible lenses and if there quality lenses should not effect the performance and should not cause heat problems as long as the light has good heat sinks.

 

[nhdtjq]

60 degree lens are pretty narrow and they will consentrate the light in a narrow beam but will limit your footprint. You might want to use some 90 degree lens around the outer two rows of diodes to widen the coverage a little.Lenses should have little effect on diode life.Alot of lights have multible lenses and if there quality lenses should not effect the performance and should not cause heat problems as long as the light has good heat sinks.

Thanks for the advice! Not sure how quality the lenses are but the look fine. I'll get some 90 deg ones for sure and reinstall them.

I have been using lensed e27 bulbs with 5w diodes and they are really strong, I can clearly see that the light doesnt blend as it hits the leaves and am a little afraid having the lenses on my main panel at a not very high level will do the same...

My tent is only 40x40x120 and I fear light from some diodes wasn't hitting the central stream at all!

 

[nhdtjq]

BTW this is what Black Dog have to say:

LEDs typically have a plastic or glass lens over the actual LED die (the name of the chip that actually produces light); this lens helps the light produced by the LED chip escape from where it is produced. Photons produced by the silicon chip (LED die) tend to be refracted back into the chip if the surface of the die is exposed to air-- plastic and glass lenses pressed against the LED die actually help these photons to leave the LED rather than refracting back into the silicon. These "primary" lenses are present on most LEDs to make them more efficient, and can be designed to focus light to different angles.

Secondary lenses for LEDs are designed to refocus the light from the diode and primary lens into a new, usually narrower beam. Many LED grow light companies are using secondary lenses and claim to "amplify", "magnify", or "boost the output of" the light. The secondary lenses are magnifying the light in exactly the same way a magnifying glass does in the sun- but no additional light is being produced or "harvested" from the LED, it is just being focused to a narrower beam or even a point. In fact, about 10% of the light is reflected or refracted by the secondary lens and is lost- but the remaining 90% gets focused into a more-intense beam.

If you're trying to market your product based on a single measurement of intensity, using secondary lenses will make the light really bright immediately under the center of the light so that any lumen, PAR, YPF or other intensity measurements taken there are impressive.

But just like a spotlight or laser, just off to the side of the narrow beam of light, there is almost no light. Any plants trying to grow in this region are only getting light reflected off the plants immediately under the light fixture-- but the grow light certainly looks impressive in an ad with its extremely high PAR value or "569% more light" due to "powerful optics"!

Our PhytoMAX and Universal Series lights use a primary LED lens designed to spread the light from each LED diode 120 degrees wide, to maximize the even coverage of our lights over their entire intended footprint to maximize your yield. We don't want the brightest grow light as measured at a single point; our lights grow plants well over their entire footprint by spreading the light out.

Secondary lenses don't "amplify" light, they lose about 10% of it and refocus the rest to make a single measurement look better on paper, to the detriment of your plants, and that's why we don't use them.

Source: https://www.blackdogled.com/faq-about-black-dog-led-lights#secondary-lenses

 

[nhdtjq]

60 degree lens are pretty narrow and they will consentrate the light in a narrow beam but will limit your footprint. You might want to use some 90 degree lens around the outer two rows of diodes to widen the coverage a little.Lenses should have little effect on diode life.Alot of lights have multible lenses and if there quality lenses should not effect the performance and should not cause heat problems as long as the light has good heat sinks.

Ive ordered some 90° ones and will get them tomorrow.

Can you please elaborate on where you believe i should place them and where to leave the 60° ones? Each board looks roughly like this:

|------x------x-----x------x------x-----x------|
|------x------x-----x------x------x-----x------|
|------x------x-----x------x------x-----x------|
|------x------x-----x------x------x-----x------|
|------x------x-----x------x------x-----x------|
|------x------x-----x------x------x-----x------|

You can copy paste that and change the letter or sommat

 

[nhdtjq]

In the end after trying various combinations I've settled on all 90, and I'll take them off for late flower.

 

[BigSm0]

what LEDs are in the black dog?

 

[nhdtjq]

what LEDs are in the black dog?

Doesnt say anything in the faq linked above. It does say they dont use lenses however, which is what the op was about...

 

[BigSm0]

I actually just got done writing up a pretty long explanation in the thread above led vs led that you should read.

As far as reflectors go the LEDs themselves are directional. Reflectors reflect light and lenses are made to intensify light but actually decrease the amount of photons as they are absorbed. All that fancy ppf and ppfd stuff. Reflectors on a led will help divert light but it also takes the light and makes it much less uniform. As light hits the reflectors its bounced all over the place vs straight down like they are intended. But they do have their place in larger areas. Smaller tents don't really benefit much from reflectors as the tent itself does the work of picking up any loose light. More importantly the LEDs being used has a much larger impact on the plants than the optics used. That's why I asked.