Light globes, often called ‘light bulbs’ or ‘lamps’ are the removable and replaceable part of a light fixture, which converts electrical energy into electromagnetic radiation and ultimately, light. While globes have traditionally been rated and marketed primarily in terms of their power consumption, expressed in watts, proliferation of lighting technology beyond the incandescent globe has eliminated the correspondence of wattage to the amount of light produced. For example, a 60 Watt incandescent light globe produces about the same amount of light as a 13 Watt compact fluorescent globe. Each of these technologies has a different efficacy in converting electrical energy to visible light. Visible light output is typically measured in lumens. This unit only quantifies the visible radiation, and excludes invisible infrared and ultraviolet light.
A wax candle produces approximately 13 lumens, a 60 watt incandescent lamp makes around 700 lumens, and a 15 Watt compact fluorescent lamp produces about 800 lumens, but actual output varies by specific design. Rating and marketing emphasis is shifting away from wattage and towards lumen output, to give the purchaser a directly applicable basis upon which to select a lamp.