ARRI LogC to ACEScg negative values

Discussions - Using ACES VFX
1

Hi,

I noticed that some ARRI log footage we are working with (dark night scene) is resulting in some negative values in ACEScg. I’m using OCIO ACES config 1.0.3 in Fusion and they will go back and forth fine however it’s a Houdini lut I’m having issues with.

The negative values in the ACEScg plate aren’t working with a lut created with bakelut. I have a fairly rudimentary understanding of luts but can see that negative source values aren’t going to work with the created houdini lut.

We aren’t quite on houdini 16 yet so I have to deal with lut bakes so is there some kind of workaround for the negative value problem?

I’m creating ACEScg plates and trying to view these with an ACEScg to ARRI log lut with a log 2 48nits shaper.

Cheers

J

2

Why not use the Arri-LogC as a shaper instead of log2 48nits? This way the negative values will return back to where they were before applying the lut.

3

Thanks Francois,

I realise now what I was doing was pointless really. (ACEScg to log as a view lut in Mplay). I discovered some pre baked luts with the OCIO ACES config so I can use them them for now.

Cheers,

John