P: sRGB Proofing Bug, with workaround, but with massive performance penalty.

Versions: All CC versions to current.

OS: Confirmed on Windows 10/11, unsure of Mac.

Reproduction:

• Open an sRGB  IEC61966-2.1 profiled image
• Set proofing profile to sRGB  IEC61966-2.1
• Turn on soft proofing
• Admire the ugly colour shift

For me the expected behaviour is... nothing should change, as the image is sRGB  IEC61966-2.1 and therefore soft proofing under that profile shouldn't yeild a change.

Workaround:

• Edit > Color settings > Desaturate Monitor Colors By :   set to 0%

Now when you enable soft proofing of a sRGB  IEC61966-2.1 image with sRGB  IEC61966-2.1 as your proof profile, no colour shift manifests.

BIG CHUFFING HOWEVER

If you do this, your performance at 100% zoom will tank to abysmal levels. Applying a curves adjustment layer, for example, will give you 1-2fps at most, even on a powerful system.

Because of the colour shift where I don't believe there should be one, it makes me anxious that the proof colour profiles aren't being applied properly in general, and obviously it's very difficult to verify if this is the case. At least with the workaround applied I have some confidence that the colour profiles are working properly, but the subsequent dropoff in performance is so steep that it's untenable.

Can anyone verify if the observed "bug" behaviour is, in fact, a bug? Or should one expect a colour shift when applying an sRGB  IEC61966-2.1 profile as a soft proof to a sRGB  IEC61966-2.1 image?