30 bit in photoshop / wide gamut - explanations needed

[Grothmog]

Hello, I just upgraded my old pc to new iMac, it's supporting 30 bit color in photoshop (option is enabled by default). It's my first time working with wide gamut monitor and this option enabled. Could someone explain me what exactly does it change? How the workflow is changed?. Most webpages mention main benefit as increasing from 256 shades to 1024. As I created new file and saw rgb as should be from 0 to 255 enabling 30 bits means increased displayed color accuracy? Does anyone know of comprehensive guide how to work with wide gamut color spaces and 30 bits?

[gener7]

This article may help: https://macperformanceguide.com/blog/2015/20151105_2300-OSX_ElCapitan-10bit-dualNEC.html

[Sahil.Chawla]

Hi there,

As you're looking for the meaning of 30 Bit inside Photoshop, this article explains it pretty well: color depth Definition from PC Magazine Encyclopedia

In comparison to other displays, a 30 bit monitor means 10 bits per channel (Red = 10, Green = 10 and Blue = 10), which is 210 = 1024. That’s 1024 colors per channel, so if we do the math 1024 x 1024 x 1024, that’s a total of 1,073,741,824 colors, which is 64 times more colors than a true color display!

It would seem that a slight increase from 8 bits to 10 bits would only slightly increase the total number of colors, but as you can see, that’s certainly not the case. So if you ever wonder what you would gain by shooting a 14-bit RAW file instead of a 12-bit, we are talking about 4.4 trillion colors vs 68.7 billion, again 64 times difference in comparison! Hence, a true 30 bit monitor is significantly better in displaying more colors than a typical 24 bit monitor.

In short, a 30 bit workflow is aimed at displaying that many colors on the screen for you to see and work with. And that’s where the problem lies, because it is not as simple as it may sound!

Regards,
Sahil

[D Fosse]

The only practical advantage is less visual banding in smooth and shallow gradients. As you say, you have 1024 individual steps per channel, instead of 256.

Imagine a staircase taking you to the first floor. It has, say, 24 steps. Then consider the very same staircase, but this time with 30 steps. It takes you to exactly the same height, but each step is a little shorter. That's what it is.

There is a misconception floating around on the internet that you need 30 bits for wide gamut displays. It's completely misunderstood. Those two are different and unrelated things.

The reality behind it is that a larger color space naturally increases the distance between a given number of individual steps. While this is true in theory, it has absolutely no significance in practice. A wide gamut unit runs just fine at 8 bit depth.

To tell you the truth, you won't see any difference with your 30 bit display compared to the standard 24 bits - unless you sit and stare at test gradients all day. In a photograph, there is always just enough noise to break up any banding. You'll only ever see the difference when you use the gradient tool in Photoshop to create synthetic gradients.

Oh, BTW - the checkbox in Photoshop just enables 30 bit output from the application. But the whole display pipeline has to support it. Do you have a NVidia Quadro  or an AM Radeon Pro card in that iMac? Standard Radeons or NVidia GeForces do not support 30 bit.

[ZBalling]

No geforce now supports 30 bit color!

[Grothmog]

Thanks for all the answers. Yes i have Radeon pro card. To sum it up as i understand it now,

8 vs 10 bits

For 8 bit monitor srgb has grayscale in 0-255 range. 8 bits has 256 channels , as i drag gradient line in photoshop i have range from 0 to 255. the values in gradient from 0 to 255 are displayed with 256 steps.

For 10 bit monitor with quadro/radeon pro  srgb has grayscale in 0-255 range. 10 bits has 1024 channels , as i drag gradient line in photoshop i have range from 0 to 255. the values in gradient from 0 to 255 are displayed with 1024 steps.

Is that correct?

[Test Screen Name]

If you are working in 8-bits per channel (the default) you can't get improvement from 30-bit display (10-bits per channel). You'd need to work in 16-bits per channel.

[Semaphoric]

I have a 10-bit card, but I keep the 10-bit feature turned off, because AMD, Microsoft, and Adobe don't play nice together with it.

[Grothmog]

yes i'm working with 16 bits per channel images

[Test Screen Name]

Then there are 32768 separate values in each channel. Don't be misled because Photoshop shows only numbers from 0 to 255; each number covers many separate colours.

[D Fosse · Accepted solution]

Yes, 16 bit data are by convention and convenience notated in 8 bit increments. So to sum up:

• An 8 bit file has 256 discrete values per channel, represented as 0-255 on any monitor.
• A 16 bit file has 32768 discrete values per channel, represented as 0-1023 on a 10 bit monitor, and 0-255 on an 8 bit monitor.