Lighting Mode Of Incandescent Lamp and Halogen Lamp

All manufacturers of incandescent, fluorescent, LED or HID lamps know that the only way to accurately know the emitted lumens is to measure in this type of integrating sphere or a related instrument, called a ”goniometer”, typically used for large complete lighting fixtures which might have sizes or shapes which can be properly tested in the sphere.

With an incandescent lamp, the light comes off the filament in virtually a 360 degree-spherical pattern (Figure 2), so only a tiny fraction reaches any point away from the lamps,

Consequently, the lumen rating of a halogen lamp is almost useless to a photographer unless he can collect most of the light heading out in every direction and redirect it forward with a focusing reflector. How much of light he can collect and how much ends up at the target depends on the size, shape, and efficiency of the reflector. The results can vary dramatically.

Simple experiments will quickly show that a tiny battery-operated LED flashlight, operating with a one-watt LED, with a narrow beam angle lens can put much more light onto a small object than a 100-watt bare incandescent light bulb—both 10 feet (about 3 meters) away.

Automobile-headlight designers have long known that precision lenses and reflectors can allow 40-50 watt lamps to project powerful beams a long-distance onto the road ahead

Virtually all professional photographers, for many years before CFL’s were available, have known what combinations of incandescent/halogen lamps and large reflectors would give then appropriate light levels.