21 Nov
2014
21 Nov
'14
3:42 p.m.
Hi all,
Finally getting back to this!
On Thu, 16 Oct 2014 16:26:53 +0200
Carsten Kurz <audiovisual(a)t-online.de> wrote:
Hmm, P3 is RGB. XYZ is XYZ.
Question, do we find a way to solve this quickly in DCP-o-matic (that
is, can we create a dependable P3->XYZ conversion matrix), or should
we suggest an alternative way to get the work done? Because I am sure
it should be possible to output plain TIFF in sRGB from Resolve even
if the project is worked on in P3, and then feed them through
DCP-o-matic with the standard sRGB-XYZ conversion.
I would have thought so, yes...
Another issue, depending on the source material,
project settings and
quality approach, is again the 8Bit issue, especially when coming
from Resolve. Any news regarding this, Carl?
Which version of Resolve is he using - platform, and version number?
The recent versions offer an EasyDCP module. This costs some money,
but at least it would solve the possible 8Bit limitation NOW, if that
is a real issue. (sorry Carl)
All 8-bit limitations should be gone in 1.76.x test versions and hence
in 1.77.0 when it is released.
Cheers,
Carl
In fact I digged up some sites and documents regarding
colour
conversion and color spaces during the last two days. My, I do have
some basic understanding from my former studies, but I guess this all
needs a lot more to fully understand all issues, and then there are
still individual software implications and limitations.
- Carsten
Am 16.10.2014 um 15:44 schrieb Carl Hetherington:
--
---------- Forwarded message ----------
Date: Wed, 15 Oct 2014 14:47:14 +0100
From: A. R. Madabushi <armadabushi(a)gmail.com>
To: Carl Hetherington <cth(a)carlh.net>
Subject: Re: [DCP-o-matic] P3 to XYZ conversion matrix (fwd)
Hi Carl thanks for the info!
The film is currently a DPX sequence in Resolve that was rendered
in P3 colour space already. My DCP program doesn’t allow me to
passthrough the file as is, without performing an XYZ transform…
which means I just need to make sure the DCP output looks the same
as the DPX sequence.
If I export TIFFs from Resolve with an XYZ LUT applied, the DCP
program will end up doing it again - so that’s XYZ conversion done
TWICE, which I want to avoid.
I found this site:
http://www.brucelindbloom.com/index.html?Eqn_RGB_XYZ_Matrix.html
…and given the info Carsten sent through I could make it…IF I
understood how to do this kind of maths!
If I can figure out the maths - I could make it work! So CLOSE!!!
On 15 Oct 2014, at 14:38, Carl Hetherington <cth(a)carlh.net> wrote:
---------- Forwarded message ----------
Date: Wed, 15 Oct 2014 15:03:08 +0200
From: Carsten Kurz <audiovisual(a)t-online.de>
To: DCP-o-matic carlh net <DCPomatic(a)carlh.net>
Subject: Re: [DCP-o-matic] P3 to XYZ conversion matrix
Maybe this helps in creating a matrix:
DCI-P3
Gamma 2.6
White point
x 0.314
y 0.351
Red
x 0.680
y 0.320
Green
x 0.265
y 0.690
Blue
x 0.150
y 0.060
From what I understand now, xyz is the storage format within
the DCP, while P3 is the color space used by DCI projector itself.
When a server plays a DCP, it transmits xyz to the projector. The
projector will convert to and show P3.
In a grading situation with a projector connected directly to
the grading workstation for realtime playout, the xyz conversion is
omited and P3 is played directly from the grading workstation into
the projector. A DCI projector therefore needs at least two
different input profiles - P3 1:1, or xyz->P3.
Now if you say you have a file sitting in P3 color space -
what does that mean? Is it the color space associated with the
editing project, or do you have a file rendered out in P3 - if so,
which container/codec?
- Carsten
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