Version of Kdenlive where bug is present (downloaded as Nightly AppImage): 20.03.70-539f6b3 (it's not present in versions list for reporting, so I chosen "git-master" as the closest). The bug appeared at least as early as in 19.04.2. To reproduce (100% repeatability): - Get .cube 3D LUT file with grid resolution 65 (see below on how to). - Create a project with any builtin profile. - Open any clip and add it to a track. - Add "Apply LUT" effect to the clip. - For "LUT file to apply" field, browse and select the .cube file. The LUT will not be applied. Grid resolution 64 and below work fine. Note that .cube file standard defines maximum grid resolution of 256. ( https://wwwimages2.adobe.com/content/dam/acom/en/products/speedgrade/cc/pdfs/cube-lut-specification-1.0.pdf ) To quickly get .cube file to test, install Argyll CMS and run (the path may differ on your platform): cd /usr/share/color/argyll/ref collink -ia -3c -r 65 ProPhoto.icm sRGB.icm test.cube Default (without "-r" key) and recommended resolution by Argyll is 65. The bug is additionally complicated to realize due to bug 415373.
Thanks for your report! With 21.04 I can not reproduce your bug. Can you please check if this is fixed for you too with the latest version/nightly?
I just checked in the latest nightly build (21.07.70-3ea8bbc), the bug in not reproducible anymore, i.e. LUT with resolution 65 and above can be successfully applied.