Is this a Pimax thing?

[Moxica]

I get these transparent shades, one for each eye.
They're worse when looking to a bright background.
Sometimes, looking at darker BG, they get a bit brighter.
Wut is dat?

(I replicated the artifact in photoshop, and it is a tad exaggerated, but they look just like that, except they are centered.)

[Nodak]

That is quadviews in action, fortunately you have options to adjust them or simply turn them off.

[MadMonty]

Try switching SSAO off in DCS