If by “output device” you mean the monitor being used when you’re working within PL (and you don’t mean the exported target file) then there’s a step missing for when SP=ON
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there’s an additional (“hidden”) process included in your “Conversion to output ICC-Profile” step.
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it’s an algorithm designed to “Protect Saturated Colors” in the conversion from W-G to the target ICC-Profile. Obviously, the “strength” (my term) of this alogorithm is specific to the target’s ICC-Profile.
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This additional algorithm is applied when SP=ON - and when actually exporting to an external target.
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However, it’s NOT applied within PL if SP=OFF.
– For the implications of that, see here: Request/Suggestion: Fix to avoid being caught-out if NOT using Soft Proofing -
It’s always applied when actually exporting to an external target regardless of whether SP=ON or OFF.
John M