A difference between Lightroom and Photoshop is usually caused by a bad display profile. Sometimes different applications can react differently to a broken profile.
Is your monitor calibrated/profiled, and if so how, using what calibrator? If not, you may have installed a bogus manufacturer profile through Windows Update (that happens a lot).
Another possibility is a buggy video driver, although that's a lot less likely. To test, turn off Graphics Processor in PS Preferences > Performance.
Using a calibrated Eizo CG276 monitor with built in calibration made by Eizo using Color Navigator 6. Just re-calibrated and the issue is still there.
OK, I'm using the same (CG246) and I've never seen this (or heard of it). Try setting ColorNavigator to making matrix profiles, not LUT (it's called "gamma" in CN - it's under "customize profile" when you set up the target). Also make sure it's v2 and not v4.
Next try disabling GPU in Photoshop.
I will try this. Where is GPU in Photoshop, I don't see it in prefs
Thanks for all your help
That worked! Didn't need to disable the GPU. THANK YOU!
That's great, but what exactly did it - matrix (gamma) profiles instead of LUT? It would be good to know for future reference.
I have seen small problems with LUT profiles in Firefox, like black clipping up to value 6 or 7, but Lightroom seems to behave well with LUT profiles here. The problem with LUT profiles is that they are "heavier" and more complex, because they contain complete tables for all possible transformations - whereas matrix profiles do it by much simpler mathematical formulae. LUT is more accurate, but matrix simpler and more reliable.
Not that I think accuracy is a problem with Eizo CGs. Which is why it's a bit puzzling that ColorNavigator has LUT as default. I use mostly matrix targets these days, my feeling is that the simpler the profile, the better.