[argyllcms] Re: widegamut LCDs and internal LUT

On Monday 22 September 2008 05:34:14 am Stefan Döhla wrote:
> Hi Alexandre,
>
> so far I'm not aware of any progress being made on this topic. When the
> thread was up on the list, I blogged on this (
> http://colorhacks.blogspot.com/2008/02/monitors-with-internal-luts.html
> ). Basically, the tool ddccontrol could be used to read and write the
> monitor's LUTs - but for this the addresses and data format would be
> necessary. Probably it's very similar to the format of the video card
> LUTs, but that's just guessed.

Most are 10 bits or 12 bits/channel.

>
> And to be more specific: I don't think you will have luck with Eizo
> displays here since they connect to the PC via USB. In contrast to this,
> e.g. NEC displays use the standard VGA/DVI cable and you can use the
> standard DDC/CI commands.

Eizo does use a USB interface for doing monitor control at least on some 
modles and one of the LProf developers has the documents for the USB interface 
from Eizo.  This includes the specs for interfacing to the interal LUTs.  Eizo 
has not authorized the public release of this document but I get the 
impression that they will make it available to other developers if they ask.  
No other vendor will make this info available to anyone as far as I can tell.  
USB Monitor HID Controls are a VESA spec that are derived from and use the 
same protocols as the DDC/CI specification.  So I suspect that it would not be 
too difficult to extend something like ddccontrol to include LUT handling 
based on the Eizo documents and this same interface might work with other 
monitors.  LUT handling however is not part of the VESA DDC/CI specification 
and is an extension that appears to be widely used by LCD vendors.  The reason 
I believe that this might work for a broad range on monitors is that the 
control chips used by ALL of the LCD vendors are only available from two 
sources and all vendors need a way to load this information during production 
and many vendors offer software that has this functionality (see below).

>
> To point 2 I would like to add, that this would certainly be nice for
> xcalib (@Graeme: you probably would agree on this for dispwin as well ;)
> )> but so far it's unclear for me how to add this without a certain
> amount of DDC/CI support inside xcalib. 

This is not needed since there is no need to load the internal LUT other than 
at the time of calibration.   Once the monitors LUTs are loaded this is 
persistant and is not lost across reboots.  IE. this makes boot loaders 
obolete.

Some other things to note about this.  Many LCD vendors offer software to 
handle calibration of the internal monitor LUT.  In some cases the software is 
free in other cases it is not.  Samsung has a free download page for thier 
software and it will work with a number of different measurement devices.  You 
need to download the version that is specific to the device and for the Huey, 
i1 Display and Sypder2 you have to use a device you purchase from Samsung or 
the software will not work.  It appears that the version for the i1 Pro will 
work with an off the self i1 Pro.  But of course you are limited to Windows 
and Mac only with this software.  

Eizo has the ColorNavigator software that can be downloaded for free.  I am 
not sure if it will work with the monitor Alexandre is considering but it does 
work with the "Graphics" monitors that Eizo sells.  The documetnation on line 
says it works with the Eye-One series, ColorMunki, DTP94, DTP94B, Spyder2 and 
Spyder3 devices.  See http://www.eizo.com/products/graphics/cn/index.asp .  
The LProf developers that has the documents from Eizo thinks that the LUT 
interface spec will work for any Eizo monitor.

Nec also has software like this and like the Eizo software it works with off 
the self meters but it is not available for free download (I think it is 
around $100). 

Hal

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