### 6.11.5 Irid_Wavelength

Iridescence calculations depend upon the dominant wavelengths of the primary colors of red, green and blue light. You may adjust the values using the global setting `irid_wavelength` as follows...

     global_settings { irid_wavelength COLOR }

The default value is `rgb <0.25,0.18,0.14>` and any filter or transmit values are ignored. These values are proportional to the wavelength of light but they represent no real world units.

In general, the default values should prove adequate but we provide this option as a means to experiment with other values.