Photoshop expert Sid Vasandani of StyleMyPic has put together a fantastic, in-depth look at luminosity masks that could significantly speed up your photo editing workflow. If you don't understand luminosity or you've never used luminosity masks, this tutorial could legitimately change the way you make selections.
Luminosity Masks have become a popular type of selections in Photoshop used by both professionals and beginners alike. However, unlike many other types of selections, they won’t be found in any menu. Instead, you’ll have to create them yourself. Don’t worry, it’s not as hard as you might think. It’s actually quite straightforward and all you need to do is follow a few simple steps.
Photoshop's tools frequently overlap, and a great example of this is Luminosity Masks vs Blend If. Both can be used to do the same thing, but they work in slightly different ways. This useful tutorial breaks down the differences so you know when and how to use each tool.