Master in Rec709 or P3

[CasaMawu]

Hi everybody, I recently discover this forum because I found myself in a big question.

First of all this is my equipment :
Macbook Pro 2018
DaVinci Resolve Studio 17.

I have to make a Master of a feature I've color grade for the festival of Vancouver : VIFF.
They asked us a DCP. And I supposed it will be projected with a P3 Projector.
I've already made the Master for web and TV in Rec709, using the "Mac Display color for viewers" since I only have my computer to view.
I know that MacBookPro Displays are good for Rec709 mastering but I'm not sure for P3-DCI.

I understand that the DCP convert the R709 color space to XYZ, and then if the projector is P3 from XYZ to P3.
Since the MacBookPro monitors have a Gamut that englobe P3, I changed the settings of Davinci to P3-DCI.
I tought I had maybe to correct a little bit the image but it is really different.

So after all that introduction here my question :

- If I leave the image in Rec709 and do my DCP like that do my image look as different as the P3 image that shows me Davinci ? Do i have to make a master in P3, and if so it can't be used with a 709 Projector ?

I have all that questions because I don't find the logic.
If DCI-P3 is a bigger Gamut than Rec709, why the color aren't the same ? Bypassing the Xenon Light of the projector. Or this color. changing is an "imitation of Xenon Light" for color grade to adapte and compensate to the correct With Point. '

Sorry for my bad english,
And sorry if it is not. understandable.

[Carsten]

The Mac P3 is not P3 in a sense as you would be able to use it as a monitoring option in Resolve. At least not without a specific calibration. If you graded versions in rec.709 - these masters are fine for DCP-o-matic. It is NOT necessary to grade in P3 in order to land on a P3 projector. DCP-o-matic will do the necessary transformation from rec.709 to X'Y'Z', and the projector will just perform it's standard X'Y'Z'->P3 transformation, without knowing wether the original source was rec.709 or P3.

It would be good if you'd find a cinema where you can check the DCP, color, and audio, before you submit.

- Carsten

[CasaMawu]

Thank you very much for the answer.
I understand, so I'm going to stick with my ODT as Rec709.
But now I'm just thinking in theory, if I do the grade in a Rec709 version 2.4 on my MacBookPro 2018 display (grading in a light controlled environment, not in "complete darkness" like in a theater), would it be better to make a 2.6 version (in "complete darkness") for the DCP, to achieve correct contrast ?

And yes, I am asking the production at least one day in a Color studio with DCI Projection to check the DCP and make any changes necessary.

Again, thank you very much for this forum, this application, and the answers

[Carsten]

You are right that it might make sense to create your DCP using a higher gamma. For many sources and editing/color grading applications, it is not well documented wether they use rec.709 (gamma 2.2) or BT.1886 (gamma 2.4). In general, coming from a rec.709/Gamma 2.2 master, you should probably use the BT.1886/gamma 2.4 color conversion in DCP-o-matic. Don't use 2.6, that is probably too much.

- Carsten

[CasaMawu]

OK ! I will follow your advice,
Thank you very much.

Lisa