NEC Display Solutions launched our first 10-bit color LCD, the 24” MultiSync PA241W, in February 2010. One of the questions that we are asked regularly by people evaluating all of our MultiSync PA Series models is “what is the difference between 8-bit color and 10-bit color?” and that is generally followed with “How do I get 10-bit color?” Ron and I have been discussing this for a while and, thanks to his feedback, we’ve put together something that I hope answers those basic questions.
Overview of LCD Color
(This is intended to give you a brief overview of the way that LCDs create color. For much more detail on LCD technologies, see the Wikipedia article on LCDs.)
Understanding how the computer creates color in an LCD is important to getting the most color from the display. Generally LCD pixels are made of 3 colored “subpixels”: red, green and blue (RGB). The LCD combines these subpixels based on the information that the computer sends over the video card. The amount of bits of color that the computer sends controls the number of colors that can be represented by the display, and the computer sends data for each of these three colors.
8 bit color: Typical desktop displays support 8 bits of color data per RGB channel. This means that there are 256 (8 bits) of possible values for each of the colors and combined the display can produce 16.8 million colors (256 x 256 x 256). This is also known as 24 bit color.
10 bit color: MultiSync PA Series displays, when used with a compatible video card, support 10 bits of color data per RGB channel. This yields 1024 values for each color and a total of 1.07 billion (1024 x 1024 x 1024) possible colors that can be represented. This is also known as 30 bit color.
Side note: older display technology featured 32-bit output. This was actually a combination of 8 bits for each RGB channel as well as an alpha (transparency) channel. Comparing this to today’s technology, 30-bit technology is true 30 bits of color data compared to the 24 bits of color data in the older, 32-bit technology.
I have a 10-bit LCD, now what?
It turns out that every element of the combination of application software, operating system, video card, video connection and display must support 10 bit color in order to achieve true 10 bit color output.
Several video cards from major manufacturers including ATI (R6xx, R7xx, R8xx ATI Radeon hardware) and NVIDIA (Quadro series with DisplayPort, not Quadro FX) support 10 bit color. In addition, you need a DisplayPort connection to connect the video card to the display.
To enable 10-bit color on NVIDIA video cards click here. [Ron – nVidia calls this feature Deep Color in their drivers]
Finally, you need both operating system and application support for 10-bit color. 10-bit color is only available on computers running Windows XP, Windows Vista and Windows 7. MacOS versions including 10.6.x do not support 10-bit color output.
Application support for 10-bit color is constantly evolving. 10-bit color is typically only supported by software that uses either OpenGL or DirectX. Contact your software vendor for questions on 10-bit color support.
Most typical desktop configurations are limited by some component in the system and can only produce 8 bit color. For example, you could have a 10-bit LCD, 10-bit capable video card, DisplayPort video connection and Windows 7 operating system but without an app that can generate 10-bit color data, you will not see the advantage of those extra bits of data. By using the correct software, an operating system, video card and display that support 10 bit color, you can produce over 1 billion colors.
If you have an NEC MultiSync PA Series display, you can download a sample application (for Windows only) to see if your system is displaying 10-bit color. [Maximize and ALT+TAB between windows for the best result]
I hope that this helps. Contact me on Twitter using @Art_Marshall or post any questions in the comments!
Art Marshall is the Product Manager for Professional Desktop Displays, including the award-winning MultiSync PA Series, at NEC Display Solutions of America.
Ron’s Reviews of NEC PA Series Displays
Photoshop & 10-bit Color Depth Support (by Ron)
While it isn’t very well documented (here’s the closest hit I found), both Photoshop CS4 & CS5 for Windows support 10-bits per channel color depth (30-bits total) by enabling the correct option in Open GL as shown in the following sections. I’m not currently aware of any support in Lightroom for this feature.
These directions will ONLY work if you are running a compatible video card using the correct cables (dual link DVI or DisplayPort) to a compatible display (like most, not all, NEC PA Series).
Enabling 10-bit Per Color Channel (30-bits total) in Photoshop CS4
Enabling 10-bit Per Color Channel (30-bits total) in Photoshop CS5
NOTE: I’ve got this working on my system before, but as of the time I wrote this article I could not get CS5 to work (CS4 on the same system worked fine). Each time it has been more challenging in CS5 to get this to work and has required multiple restarts of Photoshop to get accurate results.
Testing 10-bit Support in Photoshop
Download Ramp.psd from AMD (web search if link is broken) and open it in Photoshop. If you see this dialog:
just click OK. On a properly configured system you’ll see the correct results even using sRGB.
As the dice example above shows, in 8-bit you’ll see segments that clearly define the different shades of gray. In 10-bit per channel color you’ll see a smooth white to black gradient with no hint of any segments. If your video driver isn’t very good it can fail, and some buggy video drivers require you to restart Photoshop or even your system to get this to work properly.
NOTE: If you switch the settings on and off in a single session of Photoshop, you won’t see any changes unless you force a repaint so zoom in and then zoom back to actual pixels again to see the changes (again, ONLY on a properly function video driver).
A Word About 10-bit Per Channel Color Depth & Printing
The world of printing is way behind display technology, so Ron’s advice for those doing print soft-proofing is to DISABLE 10-bit per channel (30-bit total) color support from Photoshop. The reason why is that you’ll hide banding effects that might show in your print as many (not all) printers still only print in 8-bit using a much smaller color space, even if you enable 16-bit printing. This will result in printing surprises and therefore is not recommended.
More About High Color Support on Windows XP & Greater
To understand how and why Windows can support this advanced color mode when the Mac can not, please read this document. It helps to understand what is possible by software that may not support advanced color today. Please forward this link to your software vendor to help spread the word (i.e., educate them) on how they can add advanced color support to their products.
NEC is a partner of this blog and has provided Ron with loaner PA series displays to review (all of which have been returned). Ron also owns a NEC PA series display that he purchased at B&H with no discount or assistance from NEC. Ron may get a commission if you make a purchase using links originating from this blog.