Accurately calculating light intensity curve of your LED lights determines the best placement of the lights to ensure optimal plant growth.
To determine the light intensity of LED grow light systems correctly, you need to know the following:
- The light requirements of your plants,
- The light intensity associated with the wavelengths of light produced by the LED diodes
- The optic level of the lens used with the LED light system
Regardless of the color recipe of LEDs used in the grow lights, the light intensity curve is always bell-shaped with the 50 percent intensity level at 120 degrees, which is 60 degrees in each direction.
Figure 1. Different wavelengths of light vary in their light intensity curves, which affects optimal light placement.
If you depend on this number alone, you will make a critical mistake. Since light travels a straight line along the hypotenuse of a triangle, the light intensity decreases inversely with the square of the distance between the LED and the plant. For example, if a light travels diagonally along a 45-degree angle, the intensity of the light drops by 50 percent by the time it reaches the plant as calculated by 1.0/1.4 X1.4= 1/1.96, which rounded up is ½.
To facilitate this calculation, simply divide the relative light intensity curve by the correction factor listed in the table below:
Using Light Intensity to Determine LED Placement
To position your LED lights, follow these steps:
- Check the optic level of your LED lights
- Calculate the light intensity at various distances
- Position the LED lights at midpoint intensity
- Take into account the increase in light intensity when overlapping lights.
In addition, consider intra-canopy lighting to further optimize crop production.