Metal Halide Light Output Vs. Incandescent

Quality

• The quality of light output refers to the wavelength colors that the light produces. Sunlight produces a full spectrum of light wavelength colors, from blue to red. Artificial light is unable to reproduce the exact quality of light as the sun, therefore emitting a limited number of wavelength colors. Instead, different types of bulbs produce varying light quality, depending on the bulb. Incandescent lights generally output light waves at the red end of the spectrum. Metal halide bulbs come closest to the appearance of natural light, but have mostly blue light waves, unless they are enhanced.

Usable Light

• When incandescent lights provide light for plants, the amount of usable light is actually quite small compared to other types of bulbs, such as metal halide. According to the University of Michigan, an incandescent bulb has only about 6 to 7 percent horticulturally usable light. Metal halide bulbs, on the other hand, produce approximately three times that amount, making them a much better choice for such applications.

Metal Halide Uses

• Metal halide lights are often used in grocery stores, sports stadiums and other places where natural colors are important. It is an excellent light for use in greenhouses and home grow rooms, particularly when using special bulbs that have been enhanced to produce red light waves. This enhancement allows virtually any kind of plant to be grown under a metal halide bulb.

Incandescent Bulb Uses

• Most people are familiar with incandescent light bulbs. They are frequently used in homes, fitting into lamps, ceiling fixtures and other common locations. Although there are color-enhanced incandescent grow lights, these cannot do much more than spotlight individual plants or provide highlights for plant groupings. Incandescent bulbs get very hot, so you cannot place them within two feet of plants, limiting the amount of light plants can absorb from them.