How to write ADX to DPX

Discussions - Using ACES VFX
1

Hi,

how do I write ADX to DPX using Nuke?
We are used to produce DPX files with Nuke because the DPX format plays back very well on our old Clipster media server.
But ADX16 can create negative values that cannot be stored in DPX and result in visible clipping.
If I understand TB-2014-005 correctly this is due to two facts:

  • pixels may be darker than Dmin.
  • the APD spectral responsivities differ from the ACES primaries.

So what can I do?
What is the default Dmin value and can I adjust it in Nuke?
When I offset the images, e.g. with 0.02 before converting them from ACEScg to ADX16 I get rid of the negative values.
Is this a good solution and is there a standard to communicate this offset using DPX metadata?

Clemens