30-bit GPU for Photoshop CC

In the end I managed to pickup a Quadro K1200 for much the same price as a GTX 1050Ti (it was pulled out of a new HP Workstation).  It now gives me 1024 nice even steps in Photoshop CC, but only at zoom factors of 66.7% and above.  With a reasonable monitor you can still see the individual steps quite easily, but they are obviously a lot less noticeable.

Strangely Photoshop only appears to render 30-bit colour in 'Standard Screen Mode' and 'Full Screen Mode' but reverts to 8-bit per component in 'Full Screen With Menu Bar' mode.  Another weird quirk.

My feeling is 30-bit colour may be helpful occasionally but it's not really worth spending a lot on.  Better put it towards a monitor with decent internal calibration, so you don't suffer the banding effects introduced by the GPU LUTs.

D Fosse wrote: Yes, that is still the case. For AMD, a FirePro model is required. That said, it still may not work. I have a Quadro driving an Eizo through DisplayPort, and 10-bit color worked for the first 24 hours after installing the card, before it just went poof and permanently reverted to 8-bit mode. Haven't updated the driver in a while, though. Not that I worry about it. With a high quality monitor you really can't tell the difference in any real-world situation. You need special test gradients to see it.

Thank you for your reply.  I've also heard back from NVIDIA saying if I want 10bpc OpenGL support then I'll need a Quadro card.

I think you're right about not being able to notice the difference in most real-world situations.  However, on my existing 8bpc setup I can clearly see the steps on grads and perhaps banding is just visible in skies and skin tones.  It may be a bit more visible on my current setup, being as it's wide gamut.  I know 10bpc is not a requirement for wide gamut displays but obviously with wide gamut every step affords a somewhat greater tonal significance.

As you might expect, grads created on Photoshop at 16bpc look better when I switch to 8bpc (provided I've enabled dithering in the 'Color Settings' options).  Also, grads created at 8bpc look less stepped than those created at 16bpc, provided I've enabled dither in the grad options.  It shows the effectiveness of dithering and why processing images at 16bpc is important, even if the final output is 8bpc.

I think in the real-world other factors are more important, such as how the monitor is calibrated.  If the monitor is hardware calibrated it seems to me you don't need the GPU LUT and, unless you want to use Photoshop 30-bit display, the GPU only needs to support 8bpc output.  In other words, any modern GPU will do, provided it can support the required resolution and modest frame rate.  If the monitor calibration is handled by the PC then the GPU ought to have a LUT output depth of at least 10bpc.  I doubt it matters much visually between conveying this to the monitor over a 10bpc link or via 8bpc with dithering.  After all, it's much the same as a 10bpc display employing FRC on an 8bpc panel.  I currently have ancient AMD HD5570 cards and suspect the LUT output is only 8bpc because the banding and colouration I get in monochrome images after calibration is awful.  Whatever I end up with can't be worse than this!

Another reason for not getting too worked up about the Photoshop 30-bit display is the way layer processing reverts to 8bpc when images are viewed below 66.7%.  I've not looked into why Photoshop does this but I suspect it may date back to when processors weren't nearly so powerful.  It would be nice to have this as a user defined threshold.  Perhaps an advantage of 4k and higher screens it that we can don't have to view below 66.7% so often!