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Using a LUT post VFX on Apple Pro Res 422, originally shot on an Arri Alexa

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Dominic Stabb
Using a LUT post VFX on Apple Pro Res 422, originally shot on an Arri Alexa
on Feb 3, 2012 at 6:04:53 pm

This is quite a complicated q, any help is much appreciated!

I'm assisting on a feature on which Arri Alexa Log C Pro Res 4444 footage was originally given to me in post to apply a LUT to. I applied the 3rd party software, Alexicc11 from LightIllusion, which works very well. I had the Alexxicc LUT settings converting to MXF files at DNxHD 36.

Now we are in to the VFX stage of the film and I am supplying raw Pro Res 4444 files to the VFX guy. When he supplies his VFX back to me, also as Pro Res files, I try to apply the Alexicc LUT again but no file is created. I have concluded that this is because the original files created by the Alexa camera have an ap4h codec, but his have the standard Apple Pro Res 4444 codec.

I have tried to export Pro Res 4444 QTs from Quicktime player but they never export with this ap4h codec, and this would clearly not be ideal anyway as we would be losing picture detail. The VFX guy is having trouble exporting his VFX shots with the filter he's using - which would not match the look of our post Alexicc LUT footage anyway.

I need to supply a sequence for HD television broadcast (with VFX) next week. The TV station is going to do the grade and is happy to grade from the post Alexicc LUT DNxHD 36 MXF files.

Is this a problem that can be solved by finding a way for the VFX guy to export Pro Res files with the ap4h codec? (he is mainly using Nuke btw) Would I then be able to put his VFX shots thru Alexicc and straight in to the cut sequence for broadcast?

Once again, any help appreciated


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Jay Mahavier
Re: Using a LUT post VFX on Apple Pro Res 422, originally shot on an Arri Alexa
on Feb 10, 2012 at 6:56:53 pm

Where did you get the file for AlexICC? Generally they are LUT files that have been converted to ICC files. So there should be a regular LUT file somewhere. Get that to the VFX artist in the proper format and they should be able to apply it when rendering.

If you used one of the generic ICC profiles with AlexICC then you need to find a comparable LUT. You can probably make one. Try using the Arri LUT generator on their website. Go to

http://www.arri.com/camera/digital_cameras/tools/lut_generator.html

and select get started at the bottom. Get that LUT to the VFX artist.

Jay


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