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What’s IES?

What’s IES?

Oct 16, 2019

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 IES file can interpret it to understand how to display the correct lighting patterns on things like roads and buildings.

How to Open an IES File

IES files can be opened with Lighting Analysts’ Photometric Toolbox, Autodesk’s Architecture and Revit software, RenderZone from AutoDesSys, AcuityBrands’ Visual lighting software, and LTI Optics Photopia.

Note: If you need helping using your IES file in Revit, see Autodesk’s tutorial on how to specify an IES file for a light source.

An IES file can also be opened for free with IES Viewer, as well as online through AcuityBrands’ 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 the files are in plain text. Doing this won’t let you see any visual representation of the data though, just the text content.

Note: ISE files share the same letters as the .IES file extension. However, ISE files are either InstallShield Express Project files or Xilinx ISE Project files; they open with InstallShield and ISE Design Suite, respectively.


The EIP file extension looks similar too but are instead image files created by Capture One.

If you find that an application on your PC does try to open the IES file but it’s the wrong application or if you would rather have another installed program open IES files, see our How to Change the Default Program for a Specific File Extension guide for making that change 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 of through your web browser.

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.

Though it likely won’t be of any use, you can convert an IES file to another text-based format using the Notepad++ program I mentioned above.

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.

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 (e.g. 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.

The information in the document provided by: https://www.lifewire.com/ies-file-2621816