Exr files, png files and gamma


we are uploading exr files into shotgun through our pipeline tools, as published files.

Using this published exr file, we create a version out of it, so it can be seen by the artists easily in the Versions tab.

Problem is, the exr file’s thumbnail is not being created with the correct gamma of 1.0 (for linear exr files), instead, it assumes the file already has a gamma of 2.2 applied, and subtracts it by adding a gamma 0.4545 to it.
This works well for png and jpg files, as they are written out with a gamma of 2.2 , but this fails for exr files (or any other linear image type).

Is this a known restriction? Any plans on supporting linear image files as versions?


Hey Mario,

Would it be possible to get this (or a representative non-sensitive) sample EXR as a private message so we could investigate what may be going on here? Based on all I’ve gleaned from our engineers we aren’t doing any special transforms with EXR files for their thumbnails.

How are the EXRs being output?

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Of course! I’ll send an exr your way.


Thanks, Mario. In speaking with the engineers it sounds like the transcoding process for thumbnail generation is not reading any of the metadata from the source file, so any gamma values that may exist in the EXR are not being processed as part of the thumbnail output. The team’s now aware of the issue, though there’s no firm estimate when that behavior may change.

I’m not as familiar with the EXR format, but is there a way to “bake in” the gamma value before submitting to Shotgun?

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I am pretty sure using the OpenEXR python API, we will be able to put any metadata into the file. But as you said, that would not fix the issue right now, as the transcoder is not reading it.

We do have a workaround, so this is not a hold up for us.