Nikon D7000 manual Fluorescent Light/Other Light Sources

404 David Busch’s Nikon D7000 Guide to Digital SLR Photography

Although incandescent illumination isn’t a perfect black body radiator, it’s close enough that the color temperature of such lamps can be precisely calculated and used for photo- graphy without concerns about color variation (at least, until the very end of the lamp’s life).

Of course, old-style tungsten lamps are on the way out, to be replaced either by com- pact fluorescent lights (CFL) or newer, more energy efficient (and expensive) tungsten lights. Despite government regulations, tungsten lamps can’t be phased out completely, because CFLs don’t work in all fixtures and for all applications, such as dimmers (even if you purchase special “dimmable” CFLs), electronic timer or “dusk-to-dawn” light con- trollers, some illuminated wall switches, or with motion sensors. Only certain types of CFLs (cold cathode models) operate outside in cold weather; they emit IR signals that can confuse the remote control of your TV, air-conditioner, etc, and the typical CFL has a Color Rendering Index of 80, compared to the virtually perfect 100 rating of incandescent lights.

The other qualities of this type of lighting, such as contrast, are dependent on the dis- tance of the lamp from the subject, type of reflectors used, and other factors that I’ll explain later in this chapter.

Fluorescent Light/Other Light Sources

Fluorescent light has some advantages in terms of illumination, but some disadvantages from a photographic standpoint. This type of lamp generates light through an electro- chemical reaction that emits most of its energy as visible light, rather than heat, which is why the bulbs don’t get as hot. The type of light produced varies depending on the phosphor coatings and type of gas in the tube. So, the illumination fluorescent bulbs produce can vary widely in its characteristics.

That’s not great news for photographers. Different types of lamps have different “color temperatures” that can’t be precisely measured in degrees Kelvin, because the light isn’t produced by heating. Worse, fluorescent lamps have a discontinuous spectrum of light that can have some colors missing entirely. A particular type of tube can lack certain shades of red or other colors (see Figure 12.6), which is why fluorescent lamps and other alternative technologies such as sodium-vapor illumination can produce ghastly look- ing human skin tones. Their spectra can lack the reddish tones we associate with healthy skin and emphasize the blues and greens popular in horror movies.

Also gaining in popularity are LED light sources, particularly for movies, in the form of compact units that clip onto the camera and provide a continuous beam of light to fill in shadows indoors or out, and/or to provide the main illumination when shooting video inside.