LCD calibration.
LCD calibration.
- Subject: LCD calibration.
- From: Tom Lianza via colorsync-users <email@hidden>
- Date: Mon, 08 Jul 2019 18:01:19 -0400
- Importance: normal
Just some more discussion.
In the future implementations of Windows, and I expect Apple, if the display is
set into an HDR mode, you will probably not have access to the general video
card luts because they will not be in the HDR pipeline. At Portrait Displays we
have provide general guide lines to display vendors for design of there pipe
lines if they want us to include their displays in our CalMAN product. Florian
mentioned the unreliability of the DDC channel and that is quite correct. It
is also deadly slow. Vendors of external displays are required to supply
Portrait with a formal SDK based on our guidelines, that we use for calibration
support in our application. For low end products that do not support matrix
calibration processes, we do default to the internal Gamma Ramp functions.
I want to emphasize that using ICC color management with low end displays works
quite well with the video card lut . Graeme Gills frustration with proprietary
interfaces is well founded, but display vendors don’t want the support call
that comes with outside, third party software that can really brick the display
if not properly implemented.
Displays that offer DCI-P3 gamut MUST have a matrix in the pipeline or they
can’t image sRGB natively (but can work quite will with standard ICC color
management). In many cases they do not allow access to the matrix from
anything other than a color space selection from the display UI. In some
cases, they have calibration “slots” that can be accessed but there really is
no standard in this area that I am aware of.
The TV world is a completely different environment, particularly with respect
to UHDR specifications and use of the PQ transfer functions. TV vendors do not
want anyone fussing with the internals and the workflows are completely vendor
specific.
HDR tests are very difficult tests to run because of the need for signal
generation. You can get some oversight at https://displayhdr.org/.
Calibration of external displays capable of Dolby or HDR10+ standards require
the use of meta data.
Regards,
Tom Lianza
Vice President R&D
email@hidden
cell: 603-540 4318
Portrait Displays
6663 Owens Drive
Pleasanton, CA 94588 USA
portrait.com
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Today's Topics:
1. Printer profiling -- Enhance Matte (email@hidden)
2. Re: LCD color calibration (Florian Höch)
3. RE: Printer profiling -- Enhance Matte (Wayne Bretl)
4. Printer profiling -- Enhance Matte (email@hidden)
5. Re: LCD color calibration (Graeme Gill)
----------------------------------------------------------------------
Message: 1
Date: Sun, 07 Jul 2019 17:25:04 -0400
From: email@hidden
To: "''colorsync-users?lists.apple.com' List'"
<email@hidden>
Subject: Printer profiling -- Enhance Matte
Message-ID: <056801d5350a$728a50b0$579ef210$@videotron.ca>
Content-Type: text/plain; charset="US-ASCII"
Super, duper, exceptionally long video on printer profiling.
https://www.youtube.com/watch?v=W92nZK53B_0
Finally got a roll of Epson Enhance Matte paper!
This is my measurement: CIE Lab (M1): 95.81 1.51 -6.79.
I wanted to document the making of an ICC profile for those who have less
familiarity with ICC color management.
Best / Roger Breton
www.graxx.ca
------------------------------
Message: 2
Date: Mon, 08 Jul 2019 00:28:22 +0200
From: Florian Höch <email@hidden>
To: email@hidden
Subject: Re: LCD color calibration
Message-ID: <email@hidden>
Content-Type: text/plain; charset=utf-8
Am 07.07.2019 um 16:33 schrieb THOMAS A LIANZA via colorsync-users:
> Communication is possible to nearly all displays using some level of
> the DDC 2.0 specifications.
Not always very reliable though, and the DDC specification(s) lack
consistent implementations, which seems to prevent general applicability
(i.e. to me it looks like calibration software vendors are mostly forced
to support DDC capable displays individually and often cannot rely on a
common set of capabilities or even instruction sets).
> A wide gamut panel will necessarily have an input lookup table, a
> matrix or 3D out, followed by a display look up table.
While a matrix or 3D LUT is not a requirement, it's surely nice-to-have
for supporting things like an sRGB mode, and/or "advanced" calibration,
inside the display itself.
> In general, use of the graphic card LUT is not recommended at all
> in most modern calibration environments.
Well, we'd need to define "most". My definition of "most" with regards
to (computer) display calibration would encompass typical desktop
systems which either run a version of Windows (very common), macOS (less
common) or an open source desktop (e.g. GNOME/KDE, even less common)
paired with a run-of-the-mill LCD monitor.
Unless Microsoft (same as Apple) decides to no longer support setting
graphics card 1D LUTs ("videoLUT") via OS APIs, I don't see this
functionality going away anytime soon, and it is still the main
functionality that most calibration packages are relying upon (due to
widespread support across different platforms).
> If a display has an HDMI interface, the graphic card LUT is normally
> inaccessible because there are a number of assumptions about the
> display color management.
Hmm. My own experience thus far has been that the actual physical
connection or even interface seems to be irrelevant regarding whether or
not typical videoLUT functionality will be available.
The only requirement really is that support for the respective
generalized OS APIs is implemented at the graphics driver level (and
there are some USB3 external "graphics cards" which indeed seem to not
implement it). Whether that means actual hardware LUTs, or emulated in
software, is up to the implementation.
> The current processes generally calibrate the displays to a given
> color space and use a very simple ICC profile to describe the
> display setup.
This assumes rather high-end display hardware though, that not everyone
owning a calibration device will have access to (certainly more common
in professional or semi-professional environments).
> As the industry moves towards HDR (high dynamic range) and Wide Gamut,
> calibration occurs in the display, not on the driving platform.
It may be a bit too early to anticipate, but FreeSync2 HDR which is
(imho) quite likely to see some adoption (with even major LCD TV vendors
onboard) seems to move in the opposite direction, with most or all HDR
processing delegated to the graphics hardware in the connected system(s).
> The ICC profile is used as a container for other information in HDR
> systems in Windows 10.
AFAIK, videoLUT still applies in HDR mode, although personally I
currently have no ability to check, lacking a HDR-capable display.
Cheers,
Florian Höch
------------------------------
Message: 3
Date: Sun, 07 Jul 2019 19:12:55 -0700
From: Wayne Bretl <email@hidden>
To: email@hidden, "''colorsync-users?lists.apple.com' List'"
<email@hidden>
Subject: RE: Printer profiling -- Enhance Matte
Message-ID: <00b701d53532$aa09e5f0$fe1db1d0$@cox.net>
Content-Type: text/plain; charset=UTF-8
YouTube says the video has been removed by the user.
-----Original Message-----
From: colorsync-users
<colorsync-users-bounces+waynebretl=email@hidden> On Behalf Of Roger
Breton via colorsync-users
Sent: Sunday, July 07, 2019 2:25 PM
To: ''colorsync-users?lists.apple.com' List' <email@hidden>
Subject: Printer profiling -- Enhance Matte
Super, duper, exceptionally long video on printer profiling.
https://www.youtube.com/watch?v=W92nZK53B_0
Finally got a roll of Epson Enhance Matte paper!
This is my measurement: CIE Lab (M1): 95.81 1.51 -6.79.
I wanted to document the making of an ICC profile for those who have less
familiarity with ICC color management.
Best / Roger Breton
www.graxx.ca
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Message: 4
Date: Sun, 07 Jul 2019 22:50:06 -0400
From: email@hidden
To: "''colorsync-users?lists.apple.com' List'"
<email@hidden>
Subject: Printer profiling -- Enhance Matte
Message-ID: <05b601d53537$da43fda0$8ecbf8e0$@videotron.ca>
Content-Type: text/plain; charset="US-ASCII"
This is the update link.
https://www.youtube.com/watch?v=aZVZ-VHTe_4
The sound was terrible.
Best / Roger Breton
www.graxx.ca
------------------------------
Message: 5
Date: Mon, 08 Jul 2019 13:58:24 +1000
From: Graeme Gill <email@hidden>
To: ColorSync List <email@hidden>
Subject: Re: LCD color calibration
Message-ID: <email@hidden>
Content-Type: text/plain; charset=windows-1252
THOMAS A LIANZA via colorsync-users wrote:
> A wide gamut panel will
> necessarily have an input lookup table, a matrix or 3D out, followed by a
> display look
> up table. In general, use of the graphic card LUT is not recommended at all
> inmost
> modern calibration environments.
Nice in theory, useless in reality, because there are no standards. There
is no standard, reliable API for discovering and manipulating a displays
internal capabilities - the display makers all play the proprietary game,
and the OS makers don't have good, reliable API's for accessing these
capabilities. In contrast, there are standard, reliable API's for accessing
video card per channel lookup tables. Given that the ICC profile format
has been sabotaged in regard to display profile absolute colorimetric intent,
the video card calibration curves are the only standard mechanism available for
software to set white point and brightness. If this is ever to
be improved, an effort at standardization amongst display makers and
OS vendors is needed, that will overcome the tendency of vendors to
be secretive and play proprietary games.
Graeme Gill.
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