Tungsten lights are actually incandescent. It is created by burning up a tungsten filament from a controlled rate in the enclosed transparent envelope. When made specifically for photography, the actual light output is high and the color temperature is managed at 3200K in just about any design. Some lamps have a blue coating on the glass which gives a shade temperature that approximates that of daylight. These are intended more to be used in mixed lighting conditions, such as joined with daylight, compared to straightforward studio use.
A lot more efficient version of tungsten lighting is the tungsten-halogen lamp. This uses exactly the same coiled tungsten filament but it burns at a much higher temperature in halogen gas. Consequently, these lamps maintain virtually the identical light output and color temperature throughout their life; they also last longer than traditional lamps and are smaller with regard to their equivalent wattage. Available wattages range from 200 to 10,000 and the most powerful are intended for cinematography; the highest normal wattage for still photographic lights is 2000. The light output is the same as that from a new tungsten lamp of traditional style with the same wattage.
The newer development, particularly relevant to photography, in which camera’s white balance settings may take care of color differences, is high-performance fluorescent. The lamps used are flicker-free, nearly as bright as tungsten, color-balanced for 5400K or 3200K, and cooler and less expensive to run.
The common types of incandescent light that are being used nowadays are: Ballancroft 2500-watt north light fitted with honeycomb or egg-crate, Lee-Lowell 800-watt Totalite with barn doors, Rank-Strand 1000-watt Polaris manual spotlight, 800-watt Arrilite, and Hedler 2000-watt videolux.
Tungsten light is easy to use, photographs the way it looks, and great for large and static subjects. However, it is extremely not bright enough to freeze fast movement and still needs blue filters.
Every incandescent light needs to be fine-tuned to have the best results. Usually, it carries its very own light housing that incorporates some kind of reflector behind the lamp. This is partly to make use of all the light radiated and partly to control the beam. The deeper and more concave the reflector, the more concentrated the beam as it is harder to spread a beam that is already tight when it leaves the housing compared to concentrate a broad beam. The most general-purpose housing has reflectors that give a spread of between about 45 and 90 degrees. Light that gives tighter concentration is intended for more specialized use.
Many housing allow some change to the beam pattern by moving the lamp in and out of the reflector or by moving reflector doors. Barn doors fitted to some housing have a slightly different effect: they cut the edges of the beam rather than concentrate it. The beam patterns from most housings show a fall-off from the center outwards; even with a well-designed reflector, there is still a powerful concentration of light in the lamp’s filament. One way of reducing this fall-off in the design of the housing is to cover the lamp from direct view with a bar or a spiller cap. If the reflector dish is big as well, the result is a degree of diffusion. Even softer but less intense light is possible if the inside of the dish is finished in white rather than bright metal.
Used alone in the studio, tungsten lamps simply need 3200K incandescent white balance. However, tungsten lighting is frequently used on location and in interiors. However, this is often used in combination with existing lighting, like daylight and fluorescent light. As a result, lighting filters are typically used for converting the color temperature or for correcting the color to that of fluorescent lamps. You could, however, use mixed lighting and post-production methods but it is best to get it right at the shoot.
The most typical filters are blue to match daylight. Full blue is 131 mired; half-blue is -68 mired; and quarter-blue is -49 mired. These filters can be obtained as heat-resistant gels, glass and dichroic. Dichroic filters are partial mirrors, reflecting red back to the lamp and passing blue. They may not be always consistent and ideally needs to be checked before use with a color-temperature meter.