A luminance mask allows you to create a local adjustment based on the luminance values of your image. These masks are great for selecting specific tones of an image.
Like all of our local adjustments, you have the ability to create the mask (but based on luminance values), feather that mask, or invert it. Once you've done that, you can enjoy the usual adjustments like exposure, blur, contrast and others.
And since we've recently added overlay support to Polarr you can now apply overlays into your mask! Play around with the new luminance mask today.