Problems associated with color materials are quite different from those encountered with black-and-white materials. In color photography, the main problem is achieving correct color balance. The principal factor involved is the color temperature of the light source being used to illuminate the subject. This color temperature provides a natural appearance to the final product. Filters for color photography are classified as light balancing, conversion, and color compensating.

LIGHT BALANCING FILTERS

Light balancing filters come in two series (not to he confused with a series that indicate physical size): the Series 81, yellowish filters, are used to lower the color temperature of a light source; and the Series 82, bluish filters, are used to raise the color temperature of light from a light source. Both series are used when a tungsten light source is used with color film.

These two series of filters permit minor adjustments in the color quality of an exposing light to obtain cooler (bluer) or warmer (more yellow) reproduction of colors; for example, when the color temperature of a tungsten light source is 3100 K and a color temperature of 3200 K is desired for the exposing light, a Series 82

Table 3-3. Light Balancing filters

color balancing filter can be used to raise the color temperature 100 K. Light balancing filters affect the entire visible spectrum of tungsten light and provide an adjustment from one Kelvin temperature to another.

When the color temperature of a tungsten light source is unknown, you can use a color temperature meter to determine it. When trying to determine what light balancing filter to use for producing a particular color temperature with a given light source, you may use the following methods:

1. Refer to the scale on a color temperature meter.

2. Refer to the tables in the Photo-Lab-Index.

3. Consult the manufacturer's publication for a particular filter or meter.

4. Consult appropriate film or filter data sheets.

Light balancing filters are Series 81 and Series 82. Refer to table 3-3 to determine light balancing filters that can be used to raise or lower the color temperature of a given color.