How Do I Activate the Range Mask Tool in Lightroom Classic CC?

I have a similar problem. I can turn the range mask on OK after applying a grad filter or adjustment brush mask. But the colour or luminance sliders (and smoothness), although active, don't do anything. I'm in CC classic 7.5 and updated to process 4. Clearly something else needs to be turned on. Any ideas?

margueritel68573033  wrote I have watched multiple videos on You Tube on how to use the Range Mask feature in Lightroom Classic CC.  I understand that it is to be used with the graduated filter, the radial filter, or the adjustment brush to tweak colour and luminosity. What these videos DON'T tell me is how to turn the feature on and off.  I can see the Range Mask in the Develop Mode  below all the adjustment brush features, but the words are  grayed out.   I would great;y appreciate it if someone could instruct me on how to turn the Range Mask on or off when I need it.

Now if you are referring to the Color and Luminance Range Mask, that is different, and as stated within an adjustment brush, the graduated filter, or the radial filter. When you first bring up one of these tools the Color and Luminance Range Mask is off, you click on it to change from off to either a Color on, or Luminance on.

https://m.youtube.com/watch?v=SFuHYJvBXIQ

First off some clarity, are you perhaps referring to the Depth Range Mask? That only works with some iPhone images.

https://m.youtube.com/watch?v=gs5tujaM3xk

Range Mask is a method to fine tune the mask that is applied by the tool. That means you have to apply the filter, or brush something, before Range Mask becomes selectable.