What Is an IES File?

How to open, edit, and convert IES files

What to Know

This article describes what IES files are, how to open one from your computer or online, and how to convert one to a different format that's compatible with other software programs.

What Is an IES File?

A file with the IES file extension is an IES Photometric file that stands for Illuminating Engineering Society. They are plain text files that contain data on light for architectural programs that can simulate light.

Lighting manufacturers might publish IES files to describe how various structures are affected by their product. The program using the file can interpret it to understand how to display the correct lighting patterns on things like roads and buildings.

IES files.

IES is also short for some technology terms that are unrelated to this file format, like integrated engineering software, incoming email solution, and incomplete or erroneous specification.

How to Open an IES File

IES files can be opened with Photometrics Pros, Photometric Toolbox, Autodesk's Architecture and Revit software, RenderZone, the Visual lighting software, and Photopia.

Another way to open one for free is with IES Viewer or LITESTAR 4D Open, or online through Visual Photometric Tool.

A simple text editor, like Notepad in Windows or one from our Best Free Text Editors list, can also open IES files because they're just plain text. Doing this won't let you see any visual representation of the data, though, just the text content.

If you find that an application on your PC does try to open the file but it's the wrong application or you'd rather have another installed program open it, learn how to change the default IES file opener in Windows.

How to Convert an IES File

An IES file can be converted to an EULUMDAT file (.LDT) using this online converter. You can also do the opposite and convert LDT to IES. Eulumdat Tools should be able to do the same thing but it works from your desktop instead.

PhotoView isn't free but can convert IES files to formats like LDT, CIE, and LTL.

The free IES Viewer mentioned above can save the file to BMP.

Although it likely won't be of any use, you can convert an IES file to another text-based format using Notepad++.

The free DIALux program can open ULD files, which are Unified Luminaire Data files—a similar format to IES. You might be able to import an IES file into that program and then save it as a ULD file.

Still Can't Open It?

It's easy to mistake one file for another if their file extensions are similar. Since IES files use three very common letters, it's likely that if your file won't open with the suggestions above, it's because you're misreading the file extension.

For example, ISE files share the same letters but they're either InstallShield Express Project files or Xilinx ISE Project files, meaning that they open with different programs (InstallShield or ISE Design Suite).

An EIP file looks similar as well but it, too, is actually completely different. If you have one of those files, it's probably an image created by Capture One.

More Information on IES

The IES file format is called such because of the Illuminating Engineering Society. It's a society that brings together lighting experts (lighting designers, consultants, engineers, sales professionals, architects, researchers, lighting equipment manufacturers, etc.) to better design lighting conditions in the real world.

It's the IES that has ultimately influenced the creation of various standards for some lighting applications, like those used in healthcare facilities, sporting environments, offices, etc. Even the National Institute of Standards and Technology has referenced publications by the IES when it comes to Optical Radiation Calibrations.

Published by IES, The Lighting Handbook: 10th Edition is the authoritative reference for lighting science.

  • What is an IES file in lighting?

    A lighting manufacturer provides an IES file, a text file describing the strength of a light source at points on a grid, and the geometry of how the lighting fixture emits the light.

  • What can I do if AGI32 won't open my IES file?

    If specific data is flawed or missing, AGi32 cannot use the file. Items that are most often problematic include an incomplete set of test angles and nadir (or zenith) candela angles not all the same. The software always provides a reason for rejecting a photometric file.

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