In a software like Adobe Photoshop, you can achieve everything in many different ways. The same is true for luminosity masks — I know five off the top of my head. In this tutorial I will show you the method I use the most frequently; the one I believe to be the most user-friendly.
In digital imaging luminosity masks are just black and white masks mapped to different tonal ranges. Their most pure forms are used mostly in landscape retouching, but they are useful for every genre. Here, I will demonstrate this technique on a landscape image downloaded from Unsplash. Use the same picture and follow along. If you want, you can skip ahead and check the video I made of this technique at the end of the post.
Before I start, I would like to mention that I am not demonstrating this technique on this particular image, because there is anything wrong with it. It simply fits with what I am about to show you.
Since layer masks are black & white, we can use this to our advantage. We will be generating them with the help of Gradient Map adjustment layers. In case you want to know a bit more about Gradient Maps, go to this post where I write about how you can use them to generate different colour grades with them.
For now, let’s create a new Gradient Map adjustment layer on top of our background layer. Go into its attributes and click on the gradient strip to end up in the Gradient Editor. In the Gradient Editor, make the left colour stop black by clicking on it and choosing black in the colour section, and make the right colour stop white using the same method.
Now, with the help of our gradient, we can dial in our first luminosity range for our mask. If you think of the current view in front of you as a mask, you know that black hides and white reveals. Hence, if we want to create a mask for our highlight range, we need to turn everything below a highlight into black. In order to achieve this, let’s move the black stop to the position of about 75%.
This essentially cuts out the mid to black range if this was a mask. However, our highlights are not clean enough. We need to turn them white somehow in order to achieve a cleaner result. It’s easy: you just have to move the white colour stop closer to the black one. I’d say around 85% would suffice.
This is our first mask — except, it’s not a mask yet. Let’s say you would want your mask to be on a Curves adjustment layer. Go ahead and create the adjustment layer and select its mask. Now go up to Image>Apply Image… and use the default values. Congrats, you’ve created your first luminosity mask!
The next step would be to create a similar mask for the blacks and shadows. I’m not going to go through that, because it’s the same steps except you need to invert the colour stops. For a blacks-to-shadows range make sure your white colour stop is on the left side and the black is on the right.
If you’ve done everything correctly, you should have a mask like this. If you have a different result, check out the video at the end of this article to see what you missed.
OK, so now you understand how you can create luminosity masks for both ranges. However, the midtones are still missing. If you try to create a mask for the midtones using two colour stops you will find it to be impossible. Therefore, we need to introduce a third colour stop.
Click right under the colour strip to create a new stop. Then, set its colour to white and the other two to black. When you are done with this, you can proceed to set your range however you like, just make sure that the white stop is always in between the black ones. The following is what I have for the mid-range.
It’s done. This is how I like creating luminosity masks. Here is a before/after to show you how powerful a couple of luminosity masks can be when applied to a landscape image. Check out the video at the bottom for the full process.
A couple of notes:
- Don’t forget to use Apply Image… every time you want to turn these into actual masks.
- After applying, you can slightly blur the masks to make them even smoother.
- Your values may be different. Experiment with different Gradient Maps for every image.
- You can generate more than three basic luminosity masks for your images. Create hundreds if you need them.
- You can save your Gradient Maps as presets in the Gradient Editor.