Understanding IES Lights
by Atul Dravid, India

understanding ies lights

IES stands for Illuminating Engineering Society. IES standard file format was created for the electronic transfer of photometric data over the web. It has been widely used by many lighting manufacturers and is one of the industry standards in photometric data distribution. An IES file is basically the measurement of distribution of light (intensity) stored in ASCII format. You can think of it as a digital profile of a real world light. In 3d software like 3ds max it can be used for creating lights with shapes and physically accurate form.

IES light files are created by many major lighting manufacturers and can be downloaded freely from their sites. One of such lighting manufacturer is Lithonia Lighting (www.lithonia.com) which has an extensive library of IES files in different categories.

You can use an IES Viewer to view these files in a diagrammatic representation for easy understanding.

ies lights
Diagrammatic representation of different IES Lights with their Renders

There are lots of such viewers out there but I recommend the one by Andrey Legotin. It is the most well programmed IES Viewer with a Render option that shows you how a particular light would look. Download from here

ies viewer
A screenshot of an IES Viewer by Andrey Legotin

IES in 3ds Max

3ds max is one of the 3d software around which supports the use of IES lights. There are two built in IES Lights in 3ds max under the Photometric Lights panel. They are IES Sun & IES Sky. IES Sun is a physically-based light object that simulates sunlight whereas IES Sky simulates atmospheric effects on skylight. For more about these two lights, you can refer to the 3ds max documentation. 3ds max also allows you to use external IES files through its Photometric Web feature. A Photometric Web is a 3D representation of the light intensity distribution of a light source. This lets you create lights with accurate intensities as per the recorded light profiles.

ies lights
Same scene rendered with different IES Lights

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