I'm sorry for the dumb question … but can't seem to find an answer in docs…
Starting version 18 we've got (thanks SideFX) 2d zoom, which is great!
Along with it when zooming out using Ctr+Right Click (wide camera angle) there is grey area shows up indicating 2d mode, I'm not sure…
So the question is how to rid of that grey zone? I was trying to find it in display settings but didn't find anything.

click on the button with red circle next to 2D mode button

tamte
click on the button with red circle next to 2D mode button

Thanks Tomas,
Doesn’t it reset the viewport zoom?
I just need to switch off that grey colored overlay.

Take a look at Display Options > View > View Mask Opacity

DaJuice
Take a look at Display Options > View > View Mask Opacity

Worked! Thanks Siavash !