iMac P3 Display


I am using an iMac with a built in P3 display. These are using a color space commonly referred to as P3D65, with P3 primaries, D65 whitepoint, and sRGB gamma. ACES1.1 includes a new profile called P3D65, and as it is using the D65 whitepoint, I assumed if was targeted towards desktop monitors, rather than cinema projectors. Though, it is apparently using a 2.6 gamma. What is the reason for this? Is there any practical use case for a D65, 2.6 gamma combination? For now, I modified the profile, adding a 2.6->sRGB gamma correction at the end. Could you modify the P3D65 to use an sRGB gamma, or add a new profile, so that iMac monitors are supported?




HI Patrik,

Welcome! and thanks for your first post. :slight_smile:

Steve Tobenkin
ACESCentral Admin

You raise an interesting point. There is a case for the addition of an ODT for Apple Display P3. As well as a change of transfer function from 2.6 gamma to sRGB, it would probably need the addition of the “dark to dim” correction present in the sRGB and Rec. 709 ODTs, as the intended viewing environment for Display P3 is different to the cinema environment for P3-D65.

However a counter argument would be that Display P3 is not a “video standard”, so I am not sure if there is a way to create a movie file in that colour space, and be sure that it will play back as intended on an Apple P3 display, never mind on a different display such as sRGB. In theory a QuickTime or MP4 with appropriate metadata would be dealt with correctly by QuickTime colour management. But I would not be confident of that without considerable testing.

Currently the approach I would suggest for creating a wide gamut movie for playback on a Display P3 device such as an iMac, MacBook Pro or iPhone, would be to use the “Rec. 2020 P3-D65 limited 100 nits dim” ODT, and tag the movie accordingly. That is a video standard (P3-D65 in a Rec. 2020 container) so a colour managed player should play that back correctly on a Display P3 screen.

1 Like

Thank you for your reply. In my case, I am using the Apple P3 monitor for display while doing look dev in Maya and Clarisse, and comping in Nuke, so I need a “viewer” profile with as good a match as possible. I tried the profile you mentioned, but the gamma does not match. How would I go about adding dark-to-dim correction to my custom profile (P3D65+gamma correction to sRGB)?

Sorry if I wasn’t clear. The use of the Rec.2020 ODT would only be for making a movie for playback in a colour managed player (such as QuickTime Player) which transforms the image as necessary for the display in use.

If you want to view the output of the ODT directly on your Display P3 monitor, you will need a custom ODT. Are you using OCIO and modifying the config to create your custom view profile? If you are familiar with the workings of OCIO, it is possible to edit the config to add a Display P3 Output Transform, which could be done (for example) by duplicating the ACES 1.0 Output - Rec.2020 (P3D65 Limited) Output Transform and adding a few extra lines to its from_reference transform. These would be:

1. An <ExponentTransform> from 2.4 gamma to linear
2. A <MatrixTransform> from Rec.2020 to P3D65 (you can calculate the matrix using Nuke's ColorSpace node)
3. A <FileTransform> applying `linear_to_sRGB.spi1d`
1 Like