Incandescent Light

With so many different parameters to be balanced in each lamp, it is no wonder that thousands of different lamps are available for a myriad of purposes. Large lamps (including general purpose lamps), miniature lamps (such as Christmas tree lights), and photographic lamps (such as those for shooting movies) cover the three major classes of lamp.

General service lamps are made in ranges from 10 W to 1500 W. The higher-wattage lamps tend to be more efficient at producing light, so it is more energy-efficient to operate one 100-W bulb than two 50-W bulbs. On the other hand, long-life bulbs (which provide longer lifetimes by reducing the filament temperature) are less efficient than regular bulbs but may be worth using in situations where changing the bulb is a bother or may a hazard.

Spotlights and floodlights generally require accurately positioned, compact filaments. Reflectorized bulbs, such as those used for car headlights (these are tungsten-halogen bulbs) or overhead downlights (such as those used in track lighting) are made with reflectors built into the bulb: The bulb's shape along one side is designed so that a reflective coating on that inner surface shapes the light into a beam.

Lamps used for color photography have to provide a good color balance, keep the same balance throughout their lives, and interact well with the film's sensitivity. These lamps tend to be classified according to their color temperatures, which range from 5,301°F (2,927°C) for photography, 5,571°F (3,077°C) for professional movies, to 8,541°F (4,727°C) for "daylight blue" lamps, and even some "photographic blue" lamps that approximate sunshine and have a color temperature of 9,441°F (5,227°C).