Mask Visualization in Color Balance RGB

[newbie (AT)]

Can anyone tell me how to use the mask to visualize the shadow/highlights etc in color balance RGB with the checker pattern? I can not seem to clearly identify them.

It may just be me but any help or trick would be appreciated.

[Thomas_Do (Thomas)]

In the image blow I activated the highlight mask. The parts with the checker pattern are not selcted, the parts of the image you can see are selected.

Edit: If you change both checker board color to black, it might be more intuitive.