Color shift converting Prophoto 16 to sRGB 8

[Hollis1]

Hi,

I have done all my photo editing in Prophoto 16-bit for so long now, I cannot remember why I chose this profile for editing. I've never noticed a problem and I'm not sure if it's just me, but I've recently noticed a color shift at the final stage of my process when I convert the profile to 8-bit sRGB.

Here is a sample of what I'm talking about

This is from Photoshop 21.1.1 (latest release)

1. Picked a point with the color sampler while in Prophoto RGB 16-bit (top screenshot)
2. Execute a simple script that:
   1. Merges visible layers
   2. Converts bit depth to 8-bit
   3. Converts Profile to sRGB - relative colormetric, Blackpoint compensation with Dither (also tried other modes but it made no difference)
3. took bottom screenshot

I've only noticed this shift in blues.

Has anyone else noticed this or perhaps have a solution.

PS before anyone asks, I'm using a calibrated monitor :-)

[Doug Nelson]

Have you tried Absolute Colormetric? That tries to map to exact colors.

Some shift is unavoidable, as it is in printing. You're moving from a huge color gamut to one of the tiniest. As you can see here almost all the loss is in blues.

488px-CIE1931xy_gamut_comparison.svg.png

Losing the red essentially made it darker. Have you tried disabling blackpoint compensation?

You could try opening an sRGB softproof window, and see if you can at least improve things with temp adjustments.

[Hollis1]

Thank you Doug, that certainly explains it. I'll give the softproof window a go and see if it helps. It's disappointing to lose a bit of punch but it may just come down to a decision on when or whether it really matters in the grand scheme of things.