Color change between 8-bit and 16-bit

[scotwllm]

This was a surprise. I copied a layer from a 8-bit file with color blocks, including three brown ones named coffee brown, dark chocolate brown, and mahogany. In other words, they're unmistakably brown. 

I copied the layer into a 16-bit file. All the colors are a little bit different, except that the browns turned red. 

I color sampled them, and Photoshop says they're the same colors. Coffee brown is 184/77/76 in the original 8-bit and when copied into the 16-bit document. However, when I screengrabbed them, Photoshop reports the 16-bit coffee brown is RGB 250/32/79. 

I thought, if anything, the 16-bit color would be more accurate or complex than 8-bit, but that's clearly not the case, at least when it comes to browns.  I'm using an Acer CM3271K (4K UHD IPS, 99% Adobe RGB, Delta E <2 color accuracy). 

I don't know how to handle this. I can't just avoid using brown.

Scott

[c.pfaffenbichler]

What are the two images’ Color Spaces? (I mean »Color Spaces« as in ICC Profiles, not »Color Modes« as in »RGB«.)

Please set the Status Bar to »Document Profile« and post screenshots of the source image and the receiving image. 

[c.pfaffenbichler]

»However, when I screengrabbed them, Photoshop reports the 16-bit coffee brown is RGB 250/32/79.«

What are the readings for the 8bit image? 

In a Color Managed situation it would seem very unlikely that a screenshot would display the same RGB-values as in the original profiled image (except for special cases close to extremes). 

What are Photoshop’s Edit Color Settings? 

[D Fosse · Accepted solution]

This has nothing to do with 8 bit vs 16 bit. It's lack of color management procedure.

First, make sure the file has an embedded color profile. It's not so important which one, as long as there is one. Never work with untagged images (no color profile). If you need a different color space than the embedded, convert.

Second, screenshots are a special case. A screenshot is no longer in the original document color space. The numbers have been converted into the monitor profile, into monitor color space.

To correctly handle a screenshot, always assign your monitor profile first, then convert into whatever standard color space you're working in.

[c.pfaffenbichler]

If only »Document profile« was the Status Bar default then one might be able to gather the relevant information from screenshots right away in cases like this … 

[D Fosse]

Indeed. That's a lot more useful than image sizes. And it would save us a lot of time.

[scotwllm]

Thanks, D. How do I assign my monitor profile to screengrabs?

Scott

[D Fosse]

Open the screenshot in Photoshop and Edit > Assign Profile. Open the rolldown and find your monitor profile, and pick that.

At this point you will see the colors "snap" into the correct representation. But you don't want to keep it in this profile, because it's a non-standard profile specific to your screen, and it doesn't have any relevance elsewhere.

So then you convert to a standard color space, usually sRGB (or Adobe RGB or ProPhoto). You do this with Edit > Convert to Profile.

After doing this, the screenshot will match the original file both in appearance and numbers.

"Assign" changes the meaning of the existing RGB numbers, and the appearance changes accordingly. "Convert" recalculates all the numbers to preserve the visual appearance as it is.

[scotwllm]

Like this?

[D Fosse]

Yes, that's right. That's how you do it.

[scotwllm]

Thank you!

[c.pfaffenbichler]

And again: What are the two images’ Color Spaces? 

Edit: And: What are Photoshop’s Edit Color Settings? 

[c.pfaffenbichler]

Are the questions »What are the two images’ Color Spaces?« and »What are Photoshop’s Edit Color Settings?« too taxing to answer? 

[scotwllm]

I've asked you politely three, now four, times to not respond to my posts. 

[c.pfaffenbichler]

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@scotwllm wrote:

I've asked you politely three, now four, times to not respond to my posts. 

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You think I learn the names of rude Forum posters by heart in order to avoid trying to help them in other threads they might start? 

Because you seem to refer to another thread … 

But back to the issue at hand: Was the color change owed to the two images having different Color Spaces (or one being unprofiled)? 

[D Fosse]

I think this one is resolved, Christoph. It was indeed different color spaces, one being a screenshot, and yes, at least one of them was untagged, again being a screenshot. I think we can move on.