The fluorescent lamp is the only major light source that is sensitive to ambient temperatures. Light output decreases when the lamp is operated above or below optimum temperature. Most of the difference is due to the higher lamp bulb wall temperature found in 4-lamp units. Some T8 systems, for example, exhibit cold temperature characteristics of flicker and low light output when first energized. The typical commercial production ballast, however, does not provide full rated lamp lumen output.
Ballast factors vary depending on the system.
They may also vary in the field. However, the same ballast with energy saving 34-watt lamps will have a ballast factor of 0.87. Ballast factors in Canada for standard F40 lamps are typically found to be 0.93. Many papers have been written that describe the light output performance of lamps on electronic ballasts. Standard T12 systems utilizing halophosphates experience greater lumen depreciation than newer T8 lamps utilizing rare earth phosphors.