Black-and-white film, Resolve P3-DCI,


(Youngguen Kim) #1

First of all I’m sorry that My English is not so good.

I use davinci resolve 15 linux version.
I’ll grade 4K scanned dpx sequences.(scanned by Scanity)
Display is a 4K sony dci theater projector. calibrated x-0.314 y-0351
I want to use ACES color science in Resolve 15.

*Project settings
color science :ACEScc
ACES version : 1.1
IDT : ADX10
ODT : P3D60? or P3-DCI(D60 or D65 sim)?

It’s a black-and-white film, so white point is very important.
It has to be seen in monochrome.
The main output is DCP.

When I set P3-DCI(D65 sim)ODT, resolve internal vector scope shows magenta.
Projection screen is fine, I think.(it looks like rec709 d65 white)

When I set P3-D60 ODT, resolve internal vector scope shows nearly no saturation.
My projection screen shows a bit greenish.

I render DPX sequences to make DCP with clipster.

Which ODT should I use? Is DCI WP a bit greenish or just white?
It really confuses me.


(Jim Houston) #2

Yes DCI white is greenish.

Using P3D60 for cinema screen would be fine. Adjustment to make the white a little warmer grey may be necessary. Because DCI projectors vary on different sides of the screen between green and magenta, it is better to have the overall balance tilted to one side for black and white. It depends on content and how warm or cool it should appear.

Jim


(Scott Dyer) #3

Ok, what you’ve said makes sense. Let me try to explain each one and then give you a recommendation:

Ok, this makes sense. The projector is calibrated to x=0.314, y=0.351 (from here on out = “DCI white”). Resolve’s vector scope is showing you the code values being sent to the projector in RGB mode. The reason it looks “magenta” on the vector scope but ok on the screen is because in order to make a D65 white (x=0.3127 y=0.329) appear on the screen, the ODT is outputting unequal code values (magenta-ish) to counteract the green tint of the DCI white.

You can also think of it this way, “neutral” on the vector scopes shows that the code values are equal, but the vector scope doesn’t know what your projector is calibrated to. If you send equal code values to the screen when it’s calibrated to DCI white, you will get DCI white. But the ODT is labeled as P3-DCI (D65 sim). What that means is that it’s designed for the use case where you have the projector set to P3 primaries, DCI white, but want to have “neutral” ACES values appear as D65 white.

With this ODT, no compensation is done to make the white appear different. But it assumes that you have your projector set to the ACES white point (“D60”). Most people don’t calibrate their projectors to this (although we do!), so this is probably not the ODT you will want to use. You say it looks greenish which makes sense because if you actually measured the white on the screen using this ODT, it would be DCI white (0.314, 0.351) in your setup. (It shouldn’t normally be DCI white, but it will be in this instance because this is the “wrong” ODT for your display configuration)

You render DPX sequences into a DCP? If using ACES I would recommend using Resolve to export DCDM encoded TIFFs and then package those into a DCP.

DCI white is greenish. I would not recommend using that as “neutral”. I would recommend using P3-DCI (D60 sim) ODT for viewing on your projector. Again however, on the vectorscope, the neutrals will look magenta.

In ACES, a D60 white is considered ideal, but many people use D65 because it is the standard for video deliverables. Use either P3-DCI (D60 sim) or P3-DCI (D65 sim).

Before export, I would then recommend switching your output to DCDM with either (D60 limited) or (D65 limited) - corresponding to whichever you chose to grade with. This will output properly encoded X’Y’Z’ data and clip to the gamut that you used to master so that you don’t get any unexpected colors that you couldn’t see when grading. The Deliver tab can be confusing though. You don’t want to “double convert” from RGB to XYZ. This is also a danger in Clipster if you don’t have your settings right. It depends where you want to do the conversion:

  1. let the ODT handle it
  2. trust Resolve’s conversion in the “Codec” dropdown menu
  3. trust Clipster’s conversion
    Any can work but it might seem counterintuitive based on what you’re input/output are. But that’s not an ACES issue - that’s a common and general RGB-to-XYZ conversion issue…

I hope some of what I’ve said makes sense and helps you out.


(Youngguen Kim) #4

Thank you.

I understand what should I do.

And I figured out scopes and UI viewer show magenta with P3-DCI(D65 sim) odt. I generate 3D LUT(only color space transform from P3D65 to P3DCI).
I put this 3D LUT to viwer lut and scope lut I can see the neutral.

Clipster converts P3 to XYZ well but I’ll test p3dci(d60 and d65 sim)odt dpx seqs and DCDM odt tiff xyz seqs for DCP.
I know DCDM xyz tiff is more proper format for DCP. But my client wants DCDM as RGB dpx seqs. I think it’s wierd.