Tiffen FL-D - filter - light balancing - 77 mm

Since filters never actually add color, but only absorb certain wavelengths to increase the relative proportion of others, the original light source must have the colors you want in it to start with. Some sources are totally deficient in certain wavelengths, which cannot be added back using only filters. This is particularly true of many types of metal halide lighting. With other lighting types, such as fluorescent, color temperature measurements may not provide the correct filter requirements since color temperature theory is based on having a continuous spectrum, meaning light at all wavelengths. It is possible for a light source to have a sufficient spectral distribution to emulate a correctable color temperature when so measured, but its effect on film can be very different. Fluorescent lighting generally produces a greenish color overcast. Each of the many lamp types varies in color, and it can be difficult to know the precise correction even with a color temperature meter, a set of CC filters, and running some tests. There is available, however, a filter type developed as an average correction for the most commonly encountered fluorescent lamps. As produced by Tiffen, this filter is called the FL-D, for use with daylight corrected media. It is designed to yield good-to-excellent color under fluorescents, without the need for a meter and a variety of CC filters.