10-bit display: what are we talking about ?
In some very special cases that we will identify below, we can technically end up with tone breaks that a 10-bit display can smooth if we have a 10-bit compatible graphics card (in addition to a recent operating system, a compatible screen, etc.).
Key point ! The 10-bit display is only of real interest in a particular case that is clearly identified and of great interest to professional retouchers. It was created for this purpose. Not to be the miraculous answer to all our shade breaks that would turn into beautiful gradients with this magic trick, so except in this particular case, you may never see its value. So don't rush into it...
But what exactly and concretely is this about ?
Usually, when you make a grayscale in Photoshop like below (600 pixels on the side like here), you get a very nice and very progressive color chart, even in 8 bits. Obviously, this will depend a lot on your screen (and not on your graphics card).
Important ! It is not necessary to have a 10-bit graphics card to get a nice gradient in Photoshop as below. I made it in 8 bits and it displays perfectly smooth with my 8 bits card. The 10-bit display does not always tighten (the 8-bit display is sufficient) but is there to solve a particular case that professional retouchers are well aware of and that we will study below.