I can't speak for Mac's since I don't really follow that technology, but this is not true in the Windows world. I'm not aware of any video cards that can actually output 10-bits per channel color. Some of the NVidia Quadro cards mention 10-bit color in the marketing materials, but it's not clear what they actually mean by that. Saying that monitors are capable of receiving 10-bit is also a bit of a stretch. The DreamColor is being touted as the first "affordable" display with deep color and it costs $3500. None of Eizo's current displays support 10-bit color, for instance. And even if you have a DreamColor display you can't actually feed it 10-bit color from a Windows PC yet AFAIK.
The ATI X1900 series video cards that came out two years ago support 10 bit color output.http://ati.amd.com/products/radeonx1900/specs.html
Flexible display support
Dual integrated dual-link DVI transmitters
DVI 1.0 compliant / HDMI interoperable and HDCP ready*
Dual integrated 10 bit per channel 400 MHz DACs
16 bit per channel floating point HDR and 10 bit per channel DVI output
Programmable piecewise linear gamma correction, color correction, and color space conversion (10 bits per color)
Complete, independent color controls and video overlays for each display
High quality pre- and post-scaling engines, with underscan support for all outputs
Content-adaptive de-flicker filtering for interlaced displays
Xilleon™ TV encoder for high quality analog output
YPrPb component output for direct drive of HDTV displays
Spatial/temporal dithering enables 10-bit color quality on 8-bit and 6-bit displays
Actually, the limitation is the operating system, and you're not going to get deep color support under Windows until Windows 7 gets here (and even once it ships it will probably be a whlie before the hardware and drivers catch up and stabilize).
Who is talking about Windows? The limitation is Photoshop at this point in time.
I think you may be a bit confused here. When we refer to 10-bit color that is the number of bits per color channel, which for RGB color means a total 30 bits which is why the DreamColor is called a 30-bit display. So there's no upconverting from 10-bit to 30-bit, those are just two different terms for the same thing.
The price of the HP Dreamcolor monitor is $1999. so it is in the range of other professional monitors on the market.http://h10010.www1.hp.com/wwpc/us/en/sm/WF...67-3648397.html
True 10-bit panel to increase supported colors from 16.7 million (8-bit) to 1.07 billion colors and reduce color banding
Updatable 12-bit pre-LUT, 3x3 matrix, and post-LUT for maximum flexibility
True 10-bit drivers in the LCD panel itself, and the ability to support true 10 bits/color (30 bits/pixel) video through the DisplayPort 1.1 and HDMI 1.3 inputs.