Using masks to isolate areas for colour correction

[GGoosen1984]

Im trying to mask off an area to validate the colour in my scopes.

Ive created the mask but it seems that my Lumetri scopes dont only apply to that masked area? 

How do i force the scopes to only "look inside the mask"

Also, when i have masked how do i black out the rest of the image/video? 

[Ann Bens]

Apply the mask to the clip not the AL.

[R Neil Haugen]

As Ann notes, an Opacity mask will only work on the clip itself. You could alternatively use a Crop effect on the Adjustment Layer ... which at times is useful. But normally quicker to use Opacity on the clip.

Neil