A measure of lamp performance, as measured in median hours of burning time under ANSI test conditions. The decrease over time of lamp lumen output, caused by bulb wall blackening, phosphor exhaustion, filament depreciation, and other factors. The term generally applied to the visible energy from a source. Light is usually measured in lumens or candlepower. When light strikes a surface, it is either absorbed, reflected or transmitted.
Visible light is measured in lumens.
A motorized device which moves an HID lamp back and forth across the ceiling of a grow room to provide more even distribution of the light. LUX A standard unit of illuminance. One lux is equal to one lumen per square meter. This is the bulb to use in the first, vegetative phase of plant growth. The oldest member of the HID family, mercury vapor lamps work by arcing electricity through mercury vapor.