Light penetration - Reliable resources?
- Thread starter ziv2002
- Start date
SupraSPL
Well-Known Member
The smaller the point of light, the better it can be focused and the closer it will behave to the inverse square law.
In plain language, fluoro/PLL/induction is a very spread out source of light so it is difficult to direct it into the canopy very deeply and suffers the worst in terms of reflector losses. To some extent the bulb blocks its own reflected light. They should be as close to the canopy as possible.
HID is more concentrated so it has a very good reach although it also suffers significant reflector losses.
LEDs can be focused with lenses to get good reach or they can be used without lenses and kept very close to the canopy. They can also be used as side lighting. They emit in a cone shape so no need for reflector losses although there are significant losses if lenses are used.
Sorry I dont have any sources just drawing on the basics.
In plain language, fluoro/PLL/induction is a very spread out source of light so it is difficult to direct it into the canopy very deeply and suffers the worst in terms of reflector losses. To some extent the bulb blocks its own reflected light. They should be as close to the canopy as possible.
HID is more concentrated so it has a very good reach although it also suffers significant reflector losses.
LEDs can be focused with lenses to get good reach or they can be used without lenses and kept very close to the canopy. They can also be used as side lighting. They emit in a cone shape so no need for reflector losses although there are significant losses if lenses are used.
Sorry I dont have any sources just drawing on the basics.
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Greengenes707
Well-Known Member
Intensity and distance away from source are penetration.
The most accurate way to get intensity is with a PAR meter. All the math and losses going on at the soucre/hood/unit doesn't' matter if you use a PAR meter because it reads after all the variables have done their part already(like loss light).
LED's don't apple exactly to the inverse square law when using lenses. Collimated effect. All you need to know is you will never loose light faster than the inverse square...but you could loose it slower with lenses.
A lumen meter would work it the sources are similar in spectrum. But really isn't good unless that is all you have.
Now when comparing 2 lights intensity, height from the sensor needs to be the same or things may get misleading.
EX
Light1= 1000µmols@24"
Light2= 1000µmols@12
...same canopy intensity is the same...but the penetration isn't because of the distance from the source. Lensed led's may not apply perfectly to inverse square. but they do a succumb to light dispersion still.
The most accurate way to get intensity is with a PAR meter. All the math and losses going on at the soucre/hood/unit doesn't' matter if you use a PAR meter because it reads after all the variables have done their part already(like loss light).
LED's don't apple exactly to the inverse square law when using lenses. Collimated effect. All you need to know is you will never loose light faster than the inverse square...but you could loose it slower with lenses.
A lumen meter would work it the sources are similar in spectrum. But really isn't good unless that is all you have.
Now when comparing 2 lights intensity, height from the sensor needs to be the same or things may get misleading.
EX
Light1= 1000µmols@24"
Light2= 1000µmols@12
...same canopy intensity is the same...but the penetration isn't because of the distance from the source. Lensed led's may not apply perfectly to inverse square. but they do a succumb to light dispersion still.
SupraSPL
Well-Known Member
Unfortunately getting your hands a PAR accurate enough to trust is another story. In order to truly compare the effectiveness of a variety of light sources we need an accurate, calibrated spectroradiometer and measurements throughout the canopy like growershouse did. For most of us that will never happen so we have to rely on theory to some extent and then look at empirical results.
LEDs enjoy reduced inverse square law even without lenses which is a nice bonus for them.
LEDs enjoy reduced inverse square law even without lenses which is a nice bonus for them.
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