16 Oct
2014
16 Oct
'14
2:39 p.m.
An image sequence with proper color, already in XYZ and all! looks
like a clear opendcp workflow to me.
Can someone please refresh when dcpomatic work in 8-bit? other than
from 8-bit sources. I hope is not always.
Thanks!
Manuel AC
On Thu, Oct 16, 2014 at 10:26 AM, 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.
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)
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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