We developed two options for NorbBOTANIC PAR38 in response to a need for even lighting across a vertical garden surface (through our sister company, LiveWall).
A wide beam angle spreads the light out horizontally but not as far vertically from the lamp. A narrow beam angle allows the light to travel further. Thus, we use the 30 degree beam angle bulbs to light the upper rows of a living wall and the 15 degree beam angle bulbs are used to light the lower rows of plants.
The same priniciples apply to how far your plants are distanced from your lamp. Use the wider beam angle (30 degrees) to illuminate plants that are 3′ – 5′ from the lamp. Use the narrower beam angle (15 degrees) in fixtures mounted 5′ – 10′ from the plant canopy.