Hi Manfred,
while I’m on Windows it should be the same for you.
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As you know for web use (and often for printing services) it is recommended to export as sRGB – if you care about others.
When exporting, DO NOT select “As shot” but explicitly select “sRGB IEC61966-2.1” to avoid a profile mismatch (you may have your camera set up other than sRGB or want to keep your work in a wider color space).
Your calibrated P3 display will show the exported file correctly.
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Now, exporting with a ICC profile → … you get the option “Preserve color details”,
which when checked applies the default setting [ 50 ] from Softproof.
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While when exporting with “ICC profile → Same as Soft Proofing”,
the option is checked / grayed out → to then apply the “Preserve color details”
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from the Soft Proofing → “Advanced settings”,
where the “Intensity” is set to [ 50 ] by default, but here can be adjusted.
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The above should clear up your first question …
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while it has ‘nothing’ to do with printing & paper profiles. *)
*) paper profiles are NOT matrix-based ( → the Intensity slider / value is grayed out )
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That is, this option
is there for convenience (e.g. straight export w/o Soft Proofing),
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but use Soft Proofing when*) to have a correct Preview
- with Color Space deviations / changes
- to check Color Saturation vs Color Details/Texture **)
*) depends on several factors (pic, color space, monitor, settings, eye sight … )
**) talking about colored textures, not ‘textures’ from local contrast / sharpening
( and please see explanation / statements by @John-M )
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To your 2nd question …
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The “Protect Saturated Colors” slider ( as part of the “Color Rendering” ) → controls & affects the Color Saturation / Texture balance … and then also the subsequent export (be it with or without soft proof).
It may be helpful to consider the Export → Preserve Color Details setting as an additional correction when exporting to a smaller color space or to account for limited color and contrast reproduction when printing.
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Lastly …
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In the Nik Collection, there is no Softproof and Color changes can affect Color Space and Color Saturation / Texture balance. … Why not to check the processed pics in PL to then finally export (or print).
have fun, Wolfgang
(and sorry for this longish answer)
addendum
for more details about Nik please see → here …