Thanks for this Steve - I appreciate your perspective. I also like the "beginning of the workflow” concept. Scott Martin www.on-sight.com Imaging Science for Art

On Jan 19, 2024, at 2:01 PM, Steve Upton <notupton@chromix.com> wrote:

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On Jan 11, 2024, at 10:05 AM, Scott Martin via colorsync-users <colorsync-users@lists.apple.com> wrote: ... And yes, “over-range” lab values are real and needed! I photographed some artwork yesterday that used over-range vales...

Scott,

I understand the desire to have over-ranged Lab values but I think the idea has challenges in today's color architecture:

- The ICC PCS's (profile connection space for those unfamiliar) a* and b* dimensions are restricted to -128 -> 127

- This means all ICC profiles in the workflow, including display profiles, are restricted to the same ranges

So while I see the desire to be able to enter over-ranged values, there are no ICC profiles that have any LUT entries for dealing with the obvious gamut mapping that is going to have to occur... I'm curious how they are mapped today. I guess it's a linear process using DNG definitions

I also see the value in Lightroom allowing such over ranges as it's a "beginning of the workflow" tool that shows photographers their source color values AND maps them into the restrictions of the rest of the workflow. I can see wanting Photoshop to be able to do the same thing but it seems much riskier as users might expect (and use) those over ranges for other purposes than just importing photographs that might contain them in their DNG-defined spaces

regards,

Steve