Lighting - 3D for Graphic Designers - page 87

Photometric Light
A Photometric Light is an interesting type of hybrid between a Point Light, Area Light, and real-world en-
gineering. The brightness, falloff, and light pattern are governed by mathematical lens descriptions known
as Illuminating Engineering Society (IES) files . These files act as a digital profile of how the light behaves
in the real world. As a result of this mathematical description, an IES light casts extremely realistic light and
adds subtle nuance to an image. IES files can be found freely on the Internet, and some are available on the
sharing section at www.luxology.com .
In addition to the realistic falloff properties of Photometric Lights, volumetric lighting can also be ap-
plied. It should be noted, however, that these lights might require a high number of samples to render cleanly,
so they should be used carefully to avoid extensive render times. The example in Figure 4-8 shows a simple
scene led by a traditional Spot Light in the same scene with the Photometric Light.
Figure 4-8: A scene with a Point Light (left) and the same scene with a Photometric Light (right). Note the
subtle effect on realism that the Photometric Light adds.