How to Use the CIE GamColor™ Chromaticity Map

To determine the dominate wavelength(DWL) of a GamColor filter, draw a straight line from the coordinates of the light source you intend to use, (2848° Kelvin for incandescent or 5400° Kelvin for daylight sources), through the coordinates of the selected color to the curved edge of the CIE Chromaticity Map.

The dominant wavelength indicates the specific hue that the eye perceives from the combination of lightwaves which are present. DWL does not indicate how saturated the color is. The closer to the curved edge, the purer and darker the color will be. Closer to the light source the color will appear lighter and less saturated. Colors whose coordinates fall closer to the light source will have a higher percentage of light transmission.

Lavender and purple colors are a mixture of red and blue and they do not exist as individual spectrum colors. To determine the DWL of a color that falls in the lavender region, draw a line from the coordinates of the light source through the color filter coordinates to the (straight) 'purple' line. Continue the line in the opposite direction to the spectral curve, the color's DWL will be specified as a complementary color or a minus (571c).

You may use the GamColor CIE Chromaticity Map to select color filters and to visualize the colors you can achieve by blending them together in two separate instruments. After selecting the colors, draw a straight line between the two sets of coordinates. You may mix the color that appears along that line. Referring to your GamColor swatchbook, you can visualize those colors and determine the range that you will have when mixing the two selected colors.

Three color mixing. Select three GamColors, and using their coordinates, form a triangle. All the colors within that triangle can be blended harmoniously using the three main colors you have chosen. All of the GamColor coordinates that fall within the triangle can be reviewed in your swatchbook, and you can actually see many of the colors that you will be able to blend. This is an excellent tool to help choose colors for lighting a cyclorama. Keep in mind that you cannot create colors that fall outside the triangle. If the lighting range for your production require colors that are not within the triangle, you may have to make a different choice for your triangle of GamColor.

The Film and TV color imagery illustration shows the primary colors of the two systems and indicates the range of color which can be achieved in film or video production. This also illustrates those colors outside the triangles that cannot be achieved in film and video.

The Black Body Locus

The Black Body Locus is measured in degrees Kelvin. Indicated along the Black Body Curve are the color temperatures for candlelight or sunrise (approximately 1800° K), and household incandescent lamps at 2848°K. Most theatrical lamps are 3200°K but with line voltage drop and dimming you tend to get less. Also shown is 5400°K which is nominal daylight. Daylight color temperature will range from sunrise at 1800°K to north sky at 28,000°K.

A Black Body Radiator is a theoretical source which when chilled to minus 273°C (absolute 0) emits no energy. As the theoretical Black Body's temperature is raised, it begins to glow. At approximately 700°K (973°C) the Black Body will emit a small deep red glow which is visible to the human eye. As we raise the temperature to about 1800°K, it will have a very warm glow much like fire, candlelight or sunrise.

Incandescent light sources used in our home are approximately 2848°K. Many theatrical light sources are designed to be 3200°K unless they are long life lamps which have a lower Kelvin temperature, usually around 3000°K. If we do not apply the proper voltage or the lamps are dimmed, their Kelvin temperature will drop. As the Black Body Radiator's temperature is raised, it will get bluer in its content, and will have more and more blue energy in relation to its red energy.

5400° Kelvin has been designated as nominal noon day sun but in reality the color temperature of the sky can be much higher‹depending on the weather conditions and the time of day. The higher the Kelvin temperature, the bluer its content.