Color Management - 8 or 10 bits?

[bluefightingcat]

I am in the process of investing in a new display. I am far from an expert about color management etc. From my understanding 10bit is of course better than 8 bit because it produces less banding. However from my understanding to achieve 10 bit everything in the workflow needs to be 10 bit i.e. display connected with displayport, with 10bit GPU and 10bit OS and 10bit program.

So my first question is ASP capable of working with 10bits?

I run linux. Is linux capable of 10 bits?

BFC

[afx]

As far as I know, currently only PhotoShop is capable of using the 10bits access provided by some graphics card drivers.
No Linux video card driver I know of exposes a 10bit data path.

cheers
afx

[bluefightingcat]

It seems NVIDIA has achieved that:

http://www.phoronix.com/scan.php?page=n ... px=MTA1NzM

But I guess it would be premature to invest in a 10bit monitor. 8 bits should be fine for now.

BFC

[afx]

Interesting, I'd love to see the xdpyinfo output when a card that is supposed to be supported is attached.

But in general, I would not buy any non 10bit screen nowadays when looking for a top tier imaging screen.
Nec and Eizo both support it and I assume Quato as well. So it is just a standard attribute of the better screens anyway.

cheers
afx

[bluefightingcat]

When you mean 10 bit I assume you mean "real" 8 bit (i.e. 16.7M colours) with built in LUTs that produce 10 bit. Or have I completely misunderstood everything?

[afx]

10bit screen in the context of displayport for me is a screen that has a 10bit/channel data path between the graphics card and the screen. This of course pints to a LUT of at least 10bits/channel.

cheers
afx

[bluefightingcat]

But I don't understand the logic. You say that only photoshop is capable of using 10 bits (assuming you've got all the hardware and drivers working). So therefore it wouldn't really make sense to spend the extra cash on 10 bits would it? Or have I missed something?

BFC

[afx]

So therefore it wouldn't really make sense to spend the extra cash on 10 bits would it? Or have I missed something?

You do not pay extra for this once you reach the upper class monitors, it is the default.
There are lots more reasons to get a serious screen than the 10bit data path.

cheers
afx

[sauron]

Apparently nVidia has had 10 bit colour support since February, according to dpreview. There is a PDF available that suggests the Intel HD3000 and newer supports 10-bit colour, and this article suggests that the support has been available for linux on Intel chips since the 2.16 release of the X driver. For Radeon cards, the Evergreen family of GPUs support 10 bit output according to Wikipedia.

FWIW, my view is that Intel is the only manufacturer that provides decent graphics hardware support on Linux. The nVidia binary driver has a long legacy of problems, including many issues with colour management and multi-head, total lack of RadR support until very recently, and so forth. ATI/AMD at least provide open drivers, but they perform badly, and the documentation that was promised has been slow to appear in may cases, meaning that the latest ATI GPUs have poor support. Unless you want to play high framerate games, there's really no good reason under Linux to go with anyone other than Intel (and plenty of reasons to avoid them).

So, assuming you have a card with appropriate driver support, you'll need a monitor capable of doing 10-bit per channel, and a DisplayPort connection - DVI supports only 8-bit per channel. I think you can theoretically get HDMI to work, and possible even dual link DVI-D, but DisplayPort is going to be the best route, for practical purposes.

Under windows, your app has to have 10-bit support, as the window pipeline only allows 8-bit depth, so this is hacked around by using OpenGL calls to send higher depth graphics data. I believe X supports 10-bit happily (and a reading of man xorg.conf seems to support this) as long as the driver can provide the path to the hardware. I think this may be where the "only Photoshop supports this" idea comes from. So to answer your original questions:-

1/ Is Linux capable of 10 bit per channel - Yes, X can do this
2/ Is ASP capable of 10 bit per channel - Unknown, but may well not matter on Linux

You will need to be very careful about your video driver and card though. Hope this helps - I'd be interested to hear if anyone's tried this for real.

[afx]

2/ Is ASP capable of 10 bit per channel - Unknown, but may well not matter on Linux

I would make this a definite NO....
It would need internal changes to use 10bit output. Just because an underlying graphics driver supports it, does not mean the application automatically uses it. It would need to explicitly address a different type of visual on an X server.

cheers
afx
PS: Regarding Nvidia drivers, the latest betas suck as usual, but at least seem to allow multiple LUTs now and have some form of xrandr support, I am running 302.17 on my T520

[bluefightingcat]

The reason I started this thread is because I am having a dilemma on what display to choose. I can't afford a high end model so I am had previously decided on the Asus PA246Q (which is 10-bit). However they have come out with a new version the Asus PA248Q which happens to be 8-bit. So I am trying to understand the technology behind these displays.

BFC

[afx]

In that case I would ignore the 10bits but focus on more important aspects like evenness of illumination, color stability, black level, gamut and viewing angle.

The PA246Q seems to be quite interesting for the price point if you are willing to live with a few limitations:
http://www.prad.de/en/monitore/review/2 ... a246q.html

Did not see the newer model tested yet. I'd wait for reviews before buying.
You might get the older cheaper

cheers
afx