Why does PS show only 256 color Steps in a 16 Bit per channel workflow

Question

Hi forum-members,
I am a bit confused about the way PS (CS5) acts with colors when editing pictures (RAW-converted) in RGB 16 bit per channel mode.
(please don't mind, if I am using some wrong English expressions here - since the PS at my work is German)
--> I would expect, that I would be able to select from a variety of 65535 (=16 Bit) color steps for every R - G or B channel ... bus PS still let's me select just 256 (=8 Bit) colors per channel (in the color palette on the right - also the "color pickup tool" will show 8 Bit values - the image certainly has 48 bit color depth).
Why am I asking? I will get a display capable of displaying 10 bit colors per channel in PS (NEC PA241W, ATI FirePro V5800, DisplayPort --> 30 Bit colors in Adobe PS) next week. And thus I need a better color resolution (which would mean: 16 Bit in PS) to avoid banding-effects.
Does anybody know why I can't select more colors here or how to change this behaviour?
Thank you very much in advance for your answers!
Blendax74

Answer 1

Hi Mark,
I already managed getting it to work :-)
First I did not succeed and I had to reinstall my system (because of driver issues of the remaining nVidia driver - my old card...).
After reinstallation and performing all necessary steps (as descripbed here: http://www.amd.com/us/Documents/48108-B_ATI_FirePro_Adobe_10-Bit_FAQ_R5_Final.pdf) I now get 30 Bit color ...
... which is AMAZING! You really can see the superior quality in almost every picture. Colors are very accurate and especially in dark shadows or skys you get a much better color rendition (now its indeed hard to see the color values of a color gradient anymore...).
Also have a look at this page related to 10 Bit output: http://www.amd.com/US/PRODUCTS/WORKSTATION/GRAPHICS/TOOLS/Pages/tools.aspx
And don't forget to download 'ramp.psd' from the page above - it's a good tool to proove wether everything has worked - if you're really running on 10 Bit you will not be able to see any banding within this picture (with 8 Bit you'll see a few vertical bars... moving up to 10 Bit will result in a smooth gradient)
As with every good news there are also some annoyances (at least till now, since I think it's "only" driver problems ... so there's a good chance, things will change further in the future):
- First of all: 10 Bit per channel ONLY works with the "professional grade" graphics cards (ATI FirePro), don't try this with a Radeon type card - it simply won't work. Similarly nVidia adds 10 Bit support on display port only on the QuadFX series (very expensive!). And I just can speak for ATI FirePro cards, since this is, what I am using here. Since the cards are physically identical to the "gamer" versions I think this is a way to promote their "professional grade" cards by the vendors. (BTW: all supported ATI cards are included in the pdf mentioned above)
- ATI: with the latest ATI driver (8.7xx) will loose some abilities (OS is Windows 7, 64 Bit): first, you will loose your Aero display features, since there's some background process running that prevents Win7 from using Aero. I guess, this could be due to a lack of alpha blending capability of the driver (or hardware?) when used in 10 Bit mode. If you don't need 10 Bit it can easily be turned on and off (+ Reboot), so that the effect is NIL in "normal" operation mode.
Second I recognized some trouble using certain apps: especially playing BluRay get'S trouble, for HDCP is not detected anymore - the BluRay player tells, that HDCP is not supported by the monitor. Again, the error is gone if switching back to 8 Bit mode.
- There's no way to select the "new" colors in Adobe PS (this is - in my opinion - a bug in Adobe PS and should be fixec someday). I "worked around" this by generating a 16 Bit RGB picture with a smooth gradient --> now you can pick even the finest colors using the pipette tool... which works fine.
After all: working with 10 Bit p.C. is a great pleasure! Of course you need 16 Bit RGB pictures (which are huge sized) to get the plus in color rendition - but I am well willing to pay the price - the images are just looking great (and the PA241W is the right tool to get there - a very well made monitor! Really worth the price - equally addictive like Eizo's GC series).
Hopefully I could help you - please don't hesitate to reply if you need further assistance!
Best regards
Roland
P.S.: Yes, this forum is WAY better than most on the net - very reliable and professional support! With support of "real" Adobe engineers - congratulations, Adobe! Very much appreciated.