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Lighting Bilbo's Brief Guide to Choosing Your LED.
- Thread starter Bilbo
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And you must not forget that light distribution is much more even with led compared (in this comparison 6 cobs) to a single point source. Thats another big +.
2,1 umol/J for system efficiency.
Does 1,91 CMH account for the ballast losses and reflector losses?
If not that number gets significantly lower too.
2,1 umol/J for system efficiency.
Does 1,91 CMH account for the ballast losses and reflector losses?
If not that number gets significantly lower too.
What kind of optics? And in which way?
Generally I like reflectors for leds.
But secondary optics /lenses not so much.
- heat building up in front of the led
- if not some superopticsenhanced $$$ material it will cost atleast 8% of light, which means like 8% less bud.
- Cobs are strong point sources, means they got a lot of "penetration", opposed to e.g. single 1W diodes, so I dont see the need to focus the light
Generally I like reflectors for leds.
But secondary optics /lenses not so much.
- heat building up in front of the led
- if not some superopticsenhanced $$$ material it will cost atleast 8% of light, which means like 8% less bud.
- Cobs are strong point sources, means they got a lot of "penetration", opposed to e.g. single 1W diodes, so I dont see the need to focus the light
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Your problems are guys, you're forgetting about optics...optics make a huge difference
Please share more about optics.
It is another layer of the puzzle for me.
The HS1 has 3 layers of optics, each layer is costs about 10% of the light, right?
- the bubble over phosphor
- the plastic lens over the led
- the diffuser
Not picking on HS1, it is the only LED grow light that I have experience with.
What about COB, is that one layer of optics, just the bubble over the phosphor?
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COB is a strong light source, BUT it still needs a lens or you're throwing light in a 160 degree pattern, and losing the potential penetrative power. Ok if you're lighting a room, not so good if you're lighting an area...you're back into the realms of massive power to get even coverage...
Reflectors do not work for LED, a BIG COB has reflective potential but little reflective power, and every layer of lens loses potential as well as general luminance...so a single OPTICAL lens, will give the greatest gains and control of the light pattern most other types of lens lose efficiency in the order of 5-15%, an optical glass lens (or high grade plastic) will lose typically round 5%...
That said diffusion is good...very good, but diffusing without control and losing luminosity is a very difficult thing to achieve. Losses of 30% are not uncommon, there are some extremely good diffusion units out there that are around 12%, the cost of a sheet of this is around €890 for a large format 4mx2m sheet...
I can't comment on the HS-1 but it is proven that secondary and tertiary lenses are not optimal.
Reflectors do not work for LED, a BIG COB has reflective potential but little reflective power, and every layer of lens loses potential as well as general luminance...so a single OPTICAL lens, will give the greatest gains and control of the light pattern most other types of lens lose efficiency in the order of 5-15%, an optical glass lens (or high grade plastic) will lose typically round 5%...
That said diffusion is good...very good, but diffusing without control and losing luminosity is a very difficult thing to achieve. Losses of 30% are not uncommon, there are some extremely good diffusion units out there that are around 12%, the cost of a sheet of this is around €890 for a large format 4mx2m sheet...
I can't comment on the HS-1 but it is proven that secondary and tertiary lenses are not optimal.
So you are basically saying that, to take an example, lights designed like the MarsHydro reflector series is just a marketing gimmick and the HS1 could be improved?
I looked at some diffusion papers/studies.
My thought is that they usually dont account for the loss of light.
So they like say: 200umol vs 200umol diffused -> diffusion is good.
But what about: 200umol vs (200umol - X umol for loss of light) diffused.
Because in a greenhouse you have a "wall" and roof no matter what. And in greenhouses you have like e.g. 5 meter high ceilings and things like that, -diffusion could be beneficial there for other reason as in a cabinet homegrow.
Also I found this:
High-light grown leaves showed significant photosynthetic enhancement in direct light, while shade-adapted leaves showed no preference for direct or diffuse light at any irradiance.Highlight-grown leaves with multiple palisade layers may be adapted to better utilize direct than diffuse light, while shade leaf structure does not appear to discriminate light based on its directionality.
But:[...] Under direct beam light, leaves at the top of a canopy will usually be saturated photosynthetically while leaves located in the lower canopy are shaded and light limited. Diffuse light distributes photosynthetically active radiation more uniformly to all leaves within a canopy, enhancing the overall rate of photosynthesis
(Gu et al. 2003a).
(A new paradigm in leaf-level photosynthesis: direct and diffuse lights are not equal
http://onlinelibrary.wiley.com/doi/10.1111/j.1365-3040.2007.01751.x/pdf)
*edit. Ok here they say in a greenhouse:
Crop yield was improved when exposed to diffused light. Compared to direct light, the number of fruits increased to 7,8% and the fruit weight fared 4,8% higher. The material used to diffuse the light also reduced the light by about 4%.
http://www.robertmarvel.com/pdf/light diffusion.pdf
So I think a single point source is bad, but e.g. like 6 Cobs evenly distributed over an e.g. 3x3 area can compensate for "light saturation at top of canopy", this also gives a lot of angles to penetrate the canopy. And you could remove the lowest leaves of your plant, because every leaf that gets less light than the light-compensation-point will be a drag.
That stuff about reflectors for led not working -I totally did not get at all. Like all Cob based high bay lights usually come with a reflector.
My thought is that they usually dont account for the loss of light.
So they like say: 200umol vs 200umol diffused -> diffusion is good.
But what about: 200umol vs (200umol - X umol for loss of light) diffused.
Because in a greenhouse you have a "wall" and roof no matter what. And in greenhouses you have like e.g. 5 meter high ceilings and things like that, -diffusion could be beneficial there for other reason as in a cabinet homegrow.
Also I found this:
High-light grown leaves showed significant photosynthetic enhancement in direct light, while shade-adapted leaves showed no preference for direct or diffuse light at any irradiance.Highlight-grown leaves with multiple palisade layers may be adapted to better utilize direct than diffuse light, while shade leaf structure does not appear to discriminate light based on its directionality.
But:[...] Under direct beam light, leaves at the top of a canopy will usually be saturated photosynthetically while leaves located in the lower canopy are shaded and light limited. Diffuse light distributes photosynthetically active radiation more uniformly to all leaves within a canopy, enhancing the overall rate of photosynthesis
(Gu et al. 2003a).
(A new paradigm in leaf-level photosynthesis: direct and diffuse lights are not equal
http://onlinelibrary.wiley.com/doi/10.1111/j.1365-3040.2007.01751.x/pdf)
*edit. Ok here they say in a greenhouse:
Crop yield was improved when exposed to diffused light. Compared to direct light, the number of fruits increased to 7,8% and the fruit weight fared 4,8% higher. The material used to diffuse the light also reduced the light by about 4%.
http://www.robertmarvel.com/pdf/light diffusion.pdf
So I think a single point source is bad, but e.g. like 6 Cobs evenly distributed over an e.g. 3x3 area can compensate for "light saturation at top of canopy", this also gives a lot of angles to penetrate the canopy. And you could remove the lowest leaves of your plant, because every leaf that gets less light than the light-compensation-point will be a drag.
That stuff about reflectors for led not working -I totally did not get at all. Like all Cob based high bay lights usually come with a reflector.
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