Colorspace Transform for DCI Mastering

Stephen Birdsong -

The images inside of a Digital Cinema Package are stored in XYZ colorspace. When played from a DCI Server to a projector, the projector will transform from XYZ to P3. This means that whatever colorspace you begin with, it will be converted to P3 by way of XYZ. 

This is why it's imperative that you know the properties of your source media when mastering for DCI.

 The following properties relate to the proper colorspace transformation to XYZ.

1. Range

You need to determine whether a clip is Head range (64-940) or Full range (0-1023), and set the clip properties accordingly.

2. Color Space

The colorspaces could be RGB rec709, RGB p3, or XYZ. 

3. Gamma

The options are 2.2, 2.4, or 2.6

P3 has a standard gamma of 2.6, while rec709 is commonly 2.2 or 2.4, and in some cases even 2.5. This will be determined by the profile of the display environment during color correction. If the monitor is set to 2.2 during color timing, then the gamma encoding can be considered 2.2.  Always use "Plaingamma" for Digital Cinema Packages, not "SMPTE" gamma, even though "SMPTE" gamma is the default.



When Playing back a DCP, clipster can transform to RGB or simply remain in XYZ. You will need to configure the colorspace output settings to match your display environment. 

These can be found in:

Options/Configuration Defaults/JPEG2000/



If you use the wrong transform options going INTO a DCP, and you play it back with the same (wrong) output settings, the image will look correct on the output, but will not look correct in a DCI theatre. Two wrongs can seem to make a right. That is until you try it from a DCI server where only XYZ - P3 is performed.

 If you find that things look good out of clipster or fuze, but look like they have crushed or lifted blacks in a DCI theatre, you most likely used the incorrect transform into a DCP, and you are using that same incorrect transform back to RGB.  

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