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LED Grow Lighting
Coverage by Mounting Height
The SolarOasis Aqua-Bar
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aquariums up to 20" deep.
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|March, 2011 Volume 6, Issue 3
LED Grow Lighting Coverage by Mounting Height
This is why when we turn on a light bulb in our home- the entire room lights
up and not just the area beneath the bulb. When using these bulbs to grow
plants, a bulky external reflector is used to direct more of the light toward the
intended grow area. Even with this reflector, turning on the bulb will still
scatter light throughout the room because it is reflecting from all angles
within the external reflector. This reality makes HPS unwelcome in most
living areas and causes light pollution (aka bad neighbor relations) from
artificially lit greenhouses.
LEDs work differently.
Each individual LED is fitted
with a built-in reflector that
ensures the light shines
only where it is directed.
LED manufacturers are
able to choose the angle at
which light exits the array.
The effect of different angles of light dispersion is basically what you see
when you are using a nozzle on your garden hose. A wide angle of
dispersion causes a gentle misting over a large area, while a narrow angle
of dispersion causes a concentrated jet stream hitting a very small area.
The same amount of water comes through the hose on either setting- the
adjustment just dictates how much area the water will cover. Either the
whole plot receives a sip of water- or one plant gets blasted with the jet
stream. Most gardeners find there is a setting between these two extremes
which best serves their purpose.
In LED terms- we can take two LED arrays that are identical in light
output and give one a 180 degree beam spread and one a 14 degree beam
spread. The LED array with the 180 degree beam spread is going to cover
a much larger area but, the light is diluted through the whole 180 degrees
giving your plants a "misting" of light. The 14 degree beam spread LED
array is going to provide you with an extremely powerful stream of light but
the light would be limited to a very small area directly beneath the LEDs.
LGM LED grow lighting is designed around the middle ground. SolarOasis
incorporated two beam spreads into our products- 45 degrees and 33
degrees. The beams are narrow enough to provide a concentrated source
of light, but wide enough to cover an area much larger than the unit itself-
allowing sunlight through to the plant canopy in applications where sunlight
The LED light is exiting each cluster at one of these angles- making a
cone shaped light emission. The cone of light gets larger and larger the
further from the source. When we judge coverage on a light source such as
HPS, a 4' x 4' recommendation would suggest that this is the area that will
receive the most light. Because the light is scattering- plants outside of the
4' x 4' area are still receiving light. This is not the case with LEDs. Only
plants that are within the cone will receive light. Because of this focus, LED
grow lighting can eliminate light pollution concerns and make them more
welcome in living areas; It also makes the coverage area a very important
When determining how many LED light bars one needs- the plot size is
not the only dimension to consider. For example, let's say you are planning
an herb garden for your kitchen counter and you determine that you will
utilize a planter that is 1' wide by 3' long. While the planter only contains
seedlings- the 1' x 3' coverage would apply but you need to keep in mind
that as your plants grow- they may become larger than the planter itself so
long term coverage
considerations will need
to include an area larger
than the planter size.
This cone shape
emission is very
important to consider
as well. The base of the
cone is going to be wider
than the top. This is why
the expected height and
width of the full grown plant should be taken into consideration. As plants
get larger, only portions that fall within the light cone will grow properly.
Since much of the light emitted from the LED array is invisible to the human
eye- we have provided a chart to approximate your coverage area based on
the mounting height above the plants.
Click here for coverage area by mounting height.