Lighting Bilbo's Brief Guide to Choosing Your LED.

[MikeH]

Diffusion is GOOD, necessary in fact...but total diffusion is pretty impossible. Point source is BAD...very bad...

Lenses that produce even spread of ALL wavelengths - GOOD, individual lens on an individual LED giving a uniform beam which then mixes with other uniform beams of singular wavelengths = BAD

Big collection chamber = GOOD but hugely inefficient/weighty/expensive/hard to seal. Point source collection chamber giving uniform light output mixing with other uniform beams of multiple wavelengths = GOOD

 

[Xagor]

and why Led + Reflector (e.g. 90°) = BAD?

 

[MikeH]

COB has reflective potential but little reflective power, LED just doesn't "bounce" very well...

HiD has a 360 degree light emittance, LED is directional, therefore a reflector in a traditional environment is bouncing what would be wasted light in the direction it is supposed to go, it doesn't make vast amounts of difference to what actually arrives at a plant. Take the reflector away, it doesn't make a lot of difference...until you start talking mega money reflectors and optics.

Point in case a headlight in a car, the lamp itself is next to nothing, the optics are what make it work...and are the expensive bit.

LED is not a 360 degree emitter, it is a directional source determined by the chip itself, use the directional degree to point it where you want it...a lens does the focusing and if done correctly will impact positively on the light output. If I wanted to do a fantastic job with LED...I'd have a custom optic made, but the cost for doing that is horrendous...

 

[Corgy]

So rather than LED + reflector = BAD ..........it is really just......redundant, negligible effect ?

 

[Xagor]

COB has reflective potential but little reflective power, LED just doesn't "bounce" very well...

Hi,
that sounds interesting. Can you go more into detail/ mention some keywords of the effects so that I can dig into that?
I dont see the difference between e.g. 600nm emitted by an led compared to 600nm emitted by hps, regarding reflection/ or why it would bounce differently.
When I did some tests with reflectors they greatly increased the readings.
Without reflector one led would almost lid the whole room. With a reflector it put a spot on the wall, similar to a lense.
It gives a more even output.

 

[HubbaBubba]

headlight in a car, the lamp itself is next to nothing, the optics are what make it work

So... you are saying I should use car headlights in my grow room? Do I need the whole car or just the...
Oh, never mind. I get it.

If I wanted to do a fantastic job with LED...I'd have a custom optic made, but the cost for doing that is horrendous...

Back to serious stuff, what about copying from the Flashlight geeks.
They are already using custom TIR (total internal reflection) with LEDs.
Can that help in the the grow room?

 

[MikeH]

If you use a reflector it will of course help "shape" a beam, especially when you are talking about overall white spectrum. The human eye will "see" the predominant wavelengths...however, the beam is being shaped rather than being concentrated, you are to all intents and purposes blocking off the light from reaching an area. A bigger reflector will have a greater effect.

There are also psycho-lumen effects at play, this is a well developed sense in humans, along with psycho-acoustics, we "make up" the bits we want to see/hear, so you want to see an effect, you will see an effect. That is factual and well reported.

A reflector typically robs a beam of around 30-35% efficiency, there are very high grade reflectors that are capable of much higher reflection rates such as the TIR kit that actually get down to 5-10% efficiency losses, there are some very clever optics that work alongside these that provide negative loss figures and by intense spot magnification and internal reflection are capable of boosting beam outputs several times over.

The purpose of using a reflection for the use we want should be to concentrate a beam of light and then using a lens to put it where we want it without "prisming" or splitting the beam...for a perfectly diffuse but concentrated wash of light of the correct wavelengths where we want to put it.

Reflection for LED is difficult, maybe my statement about it being bad was misleading, but the fact is that you are taking tiny amounts of individual output, putting them together and then bouncing them around, it's just something that doesn't work very well, especially over any distance. Reflection of course "works" in the broadest sense, but simply taking Lumen Output as a result works for the human eye...it doesn't work for plants...

 

[Xagor]

I looked at some reflectors and a random 10$ ledil cree cob reflector had 94% efficiency.
And only the part of the light that that goes to the sides/bounces off the reflector gets decreased. So in total it should be much less than 6%?
How does it get robbed 35%?
http://www.ledil.com/node/2/p/16486...t=0&fr=n0&st=0&pg=0&lo=n0&ol=0&of=0&od=0&oh=0

There are also psycho-lumen effects at play, this is a well developed sense in humans, along with psycho-acoustics, we "make up" the bits we want to see/hear, so you want to see an effect, you will see an effect.

For my test I used a solar cell attached to a DMM. Both visually and on my ghetto-meter the readings increased significantly.

 

[HubbaBubba]

For my test I used a solar cell attached to a DMM

Is a DMM a Digital MultiMeter?
You used a solar cell to estimate the change in light intensity before and after the reflector, right?

 

[Xagor]

yes and yes