I would like to share a big issue of mine when creating luts in Photon and applying them in FCPX through the default lut loader. This issue makes the roundtrip with fcpx Impossible for me.

In short the video with the lut applied in FCPX appears different (darker) in comparison to the same shot's .tiff file with the lut applied in Photon.
As far as I could fiddle around it looks like a gamma 2.4/2.2 difference of sorts.

I also notice that when exporting a .tiff from FCPX and loading it in Photon it appears blueish there.

When opening the .tiff through most of the other means, the image appears like the original video file in Quicktime or inside FCPX's timeline preview.

This blueish cast when opening the file in Photon also appears if I screen grab from FCPX's timeline preview in full screen.

What I do is convert the color space of the .tiff in Photoshop to sRGB and then I work in Photon.

While you might argue that this is causing the issue I can tell you that working with the blueish cast in Photon makes the color difference even greater when back in fcpx in my opinion.

Please send help :(
@Jonathan Ochmann @Pirmin Straub