https://mattepaint.com/academy/tutorial/dynamic-masking/

Using the "blend-if" layer mode in photoshop is an incredibly powerful way to quickly mask objects based on a brightness or colour value. What's more, this method remains 'live' which means it'll adjust to future changes! What was missed when covering this video is, if you want to "apply" the effect to the layer permanently, add a new blank layer on top of the layer with blend-if applied, then merge the two. This will force photoshop to bake the effect into the layer.