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 Pas de "wide gamut" pour moi
Author: La_Maudite 
Date:   12-05-07 10:27
Je termine mon monologue.

Bien que j'ai surtout discute d'un modele en particulier (NEC 2490WUXi), je crois que ca s'applique a tous les moniteurs avec un "wide gamut" qui n'ont pas de 3D-LUT (lire ce qui suit pour savoir pourquoi). Voici donc un resume des discussions que j'ai eu sur dpreview, question de les archiver:

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http://forums.dpreview.com/forums/read.asp?forum=1004&message=25805368
Forum PC Talk
Subject Re: NEC 2490WUXi rocks! sRGB looks great.
Posted by Carl Robitaille [CLICK FOR PROFILE]
Date/Time 10:34:27 PM, Wednesday, November 28, 2007 (GMT)

Tom_Bruno wrote:
> Last week I took delivery of a NEC 2490WUXi.

Congrats on your purchase. Like you, I was going for a NEC 2690WUXi before reading this thread. So thank you very much for starting the thread and asking all the right questions, and of course thanks to everyone who contributed to this thread.

I now understand that the sRGB mode can't be calibrated and that the only way to use the 12 bits internal LUT is to use aRGB. Since I want to switch between Linux and XP, I want the colors to be accurate when using applications not color management aware. So the NEC 2690WUXi can't be a good option for me.

I read all the posts in this thread, and there is still one thing that isn't 100% clear for me. I think the NEC 2490WUXi makes possible the calibration in sRGB mode using the 12 bits internal LUT. Is it really the case??? It's not obvious from your last post, and I've read conflicting things about that. I just don't want that profile to be stored in the LUT on the graphics card.

In other words, if the standard sRGB profile is used in the by XP, does the calibration give good results? That would ensure that, when switching to Linux, the calibration would remain the same and the colors would be accurate for all applications.
What profile are you using right now in XP?

One last thing way to put it.... I want to calibrate the monitor, then connect it to a different computer and still have a calibrated monitor which is accurate for sRGB. Is it too much to ask? ;-)
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http://forums.dpreview.com/forums/read.asp?forum=1004&message=25814602
Forum PC Talk
Subject Re: NEC 2490WUXi rocks! sRGB looks great.
Posted by Will49 [CLICK FOR PROFILE]
Date/Time 3:01:55 PM, Thursday, November 29, 2007 (GMT)

Carl Robitaille wrote:
> I read all the posts in this thread, and there is still one thing
> that isn't 100% clear for me. I think the NEC 2490WUXi makes possible
> the calibration in sRGB mode using the 12 bits internal LUT. Is it
> really the case??? It's not obvious from your last post, and I've
> read conflicting things about that. I just don't want that profile
> to be stored in the LUT on the graphics card.

The sRGB mode is not calibratable on either models (it's a factory preset). However since the 2490 is basically an sRGB gamut monitor, you can calibrate the monitor in it's Programmable mode to sRGB's white point and gamma, and it will result in a "calibrated sRGB monitor".

> In other words, if the standard sRGB profile is used in the by XP,
> does the calibration give good results? That would ensure that, when
> switching to Linux, the calibration would remain the same and the
> colors would be accurate for all applications.

If your applications in Linux are all assuming an sRGB monitor, then yes this would pretty much work, even though you aren't able to install a color profile on Linux.
> One last thing way to put it.... I want to calibrate the monitor,
> then connect it to a different computer and still have a calibrated
> monitor which is accurate for sRGB. Is it too much to ask? ;-)

As long as you are using DVI (digital) video, then you can do this, since the calibration is stored in the display, not the video card. If you are using analog video you will have less accurate results.
See this thread for what to check:

http://forums.dpreview.com/forums/read.asp?forum=1004&message=25228409


--
Will Hollingworth
Manager of OEM Product Design & Development Engineering
NEC Display Solutions of America, Inc.
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http://forums.dpreview.com/forums/read.asp?forum=1004&message=25815363
Forum PC Talk
Subject Re: NEC 2490WUXi rocks! sRGB looks great.
Posted by Carl Robitaille [CLICK FOR PROFILE]
Date/Time 4:21:54 PM, Thursday, November 29, 2007 (GMT)

Hi Will,

Thanks again for the great info you provide here.

Will49 wrote:
> The sRGB mode is not calibratable on either models (it's a factory
> preset). However since the 2490 is basically an sRGB gamut monitor,
> you can calibrate the monitor in it's Programmable mode to sRGB's
> white point and gamma, and it will result in a "calibrated sRGB
> monitor".

Cool, that's what I wanted.

> If your applications in Linux are all assuming an sRGB monitor, then
> yes this would pretty much work, even though you aren't able to
> install a color profile on Linux.

My understanding is that, if no profile is used (on Linux or otherwise), sRGB is the prefered choice so that the content is displayed correctly everywhere (w/o profile attached to the file of course).

I know it's not ideal for printing, and I would have gone for a wide gamut monitor if the sRGB mode was better. I'll consider one when color management is used in all the apps and OS I use. Until then, what I need is a calibrated sRGB monitor.
> As long as you are using DVI (digital) video, then you can do this,
> since the calibration is stored in the display, not the video card.
> If you are using analog video you will have less accurate results.

Great!

> http://forums.dpreview.com/forums/read.asp?forum=1004&message=25228409

Thanks for the link. For whatever reason, it didn't show up in my searches. I'll have one last question that I'll post in the other thread.
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http://forums.dpreview.com/forums/read.asp?forum=1004&message=25815765
Forum PC Talk
Subject Re: 2690WUXi and LUTs (I wish Will from NEC would see this)
Posted by Carl Robitaille [CLICK FOR PROFILE]
Date/Time 4:41:32 PM, Thursday, November 29, 2007 (GMT)

Will49 wrote:
> Doing gamut mapping in a monitor to make it behave like it has a
> different (smaller) gamut than it actually has, requires very
> sophisticated 3D LUTs and transforms. Applying these transforms in
> the 2690 means that the LUTs are no longer available for use in
> calibrating the display with SpectraView.

That's what I don't understand. Is there a paper somewhere that I can read to understand what makes it complicated to do so? Without knowing the internal workings of the programmable LUT and SpectraView II, I think it's safe to say that the LUT is basically a mapping of 2^24 -> 2^36, mapping 8 bits RGB inputs to 12 bits RGB outputs. Since sRGB is essentially (totally?) a subset of aRGB, why can't the LUT be filled with colors matching sRGB (as close as possible of course) and using only a subset of the gamut available? Is it a software limitation like I think it is, or is there something more to it?
> If someone really needs to have an calibrated "true" sRGB display, I
> would recommend either going for the 2490, or using a standard LCD as
> a secondary display for proofing sRGB.

That's what I intend to do. But if the limitation is software, it's a shame that I'll have to "limit" myself and buy a 2490 instead of a 2690, which was my first choice.
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http://forums.dpreview.com/forums/read.asp?forum=1004&message=25818131
Forum PC Talk
Subject Re: 2690WUXi and LUTs (I wish Will from NEC would see this)
Posted by Will49 [CLICK FOR PROFILE]
Date/Time 7:33:58 PM, Thursday, November 29, 2007 (GMT)

Carl Robitaille wrote:
> That's what I don't understand. Is there a paper somewhere that I can
> read to understand what makes it complicated to do so? Without
> knowing the internal workings of the programmable LUT and SpectraView
> II, I think it's safe to say that the LUT is basically a mapping of
> 2^24 -> 2^36, mapping 8 bits RGB inputs to 12 bits RGB outputs.

Not quite. It is three 1D (red, green and blue) 8 bit (2^8) in by 12 bit out (2^12) LUTs.

> sRGB is essentially (totally?) a subset of aRGB, why can't the LUT be
> filled with colors matching sRGB (as close as possible of course) and
> using only a subset of the gamut available?

Because 1D LUTs can't map colors in the way necessary to manipulate one gamut into another. That requires a 3D LUT or sophisticated dynamic color processor.
A true 12 bit 3D LUT would need (2^12)^3 = 68719476736 entries.


--
Will Hollingworth
Manager of OEM Product Design & Development Engineering
NEC Display Solutions of America, Inc.
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http://forums.dpreview.com/forums/read.asp?forum=1004&message=25819216
Forum PC Talk
Subject Re: 2690WUXi and LUTs (I wish Will from NEC would see this)
Posted by Will49 [CLICK FOR PROFILE]
Date/Time 8:32:58 PM, Thursday, November 29, 2007 (GMT)

> A true 12 bit 3D LUT would need (2^12)^3 = 68719476736 entries.

I should clarify that an 8 bit in x 12 bit out 3D LUT would need (2^8)^3 = 16777216 12 bit values.
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http://forums.dpreview.com/forums/read.asp?forum=1004&message=25819783
Forum PC Talk
Subject Re: 2690WUXi and LUTs (I wish Will from NEC would see this)
Posted by Carl Robitaille [CLICK FOR PROFILE]
Date/Time 9:23:27 PM, Thursday, November 29, 2007 (GMT)

Will49 wrote:
> Not quite. It is three 1D (red, green and blue) 8 bit (2^8) in by 12
> bit out (2^12) LUTs.

Got it.

> Because 1D LUTs can't map colors in the way necessary to manipulate
> one gamut into another. That requires a 3D LUT or sophisticated
> dynamic color processor.

Got it. Makes sense.

> A true 12 bit 3D LUT would need (2^12)^3 = 68719476736 entries.

I see that you clarified in your replay that it would take 2^24 entries of 12 bits each. That's not that too much memory nowadays. It seems to me that it's something you should consider in your furure line of high end monitors.

Thanks again for your time. It looks like it's I'm going to buy a 2490. All I need now is to find the SV version in stock somewhere in Canada.
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 Topics Author  Date
 Monitor: multiple OS (Linux and XP), calibration, sRGB, internal LUT  new
La_Maudite 11-28-07 07:39 
 To wide-gamut, or not to wide gamut  new
La_Maudite 11-28-07 18:47 
 Pas de "wide gamut" pour moi  new
La_Maudite 12-05-07 10:27 
 Re: Pas de "wide gamut" pour moi  new
AirBete 12-05-07 10:36 
 Re: Pas de "wide gamut" pour moi  new
La_Maudite 12-07-07 10:11 
 Re: Pas de "wide gamut" pour moi  new
AirBete 12-07-07 10:56 
 Re: Pas de "wide gamut" pour moi  new
La_Maudite 12-07-07 11:01 
 Re: Pas de "wide gamut" pour moi  new
La_Maudite 12-25-07 03:28 
 Autres liens concernant le "wide gamut" et le sRGB  new
La_Maudite 12-05-07 10:47