idiot's guide to luminosity masks

An Idiot’s Guide To Making Sense of Luminosity Masks

(Updated September 2018)

Luminosity masks are highly selective, customizable selection tool in Photoshop to help you apply targeted local adjustment that blends naturally in your image.

To be able to use luminosity masks, you need:

  • 1
    To know how layer masks work.
  • 2
    To understand how brights, midtones and darks luminosity masks work.
  • 3
    To have a basic knowledge of Photoshop. (you don't need to be a master in Photoshop!)

In this tutorial, you'll start off by learning how luminosity masks work. Then, visualize the masks in gradient map and lastly, see how it is applied as a layer mask. The intention of this article it to help you make better sense of luminosity masks.

I use Adobe Photoshop, don't worry if you use other software. The steps might be different but the principles are the same.

Luminosity Masks Is A Selection Tool

Luminance, marching ants, brights, darks and midtones masks are among the words you hear with luminosity masks.

marching ants luminosity masks

Now, I want you to forget about these just for a minute.

All I want you to know for the time being is that it is a selection tool and a layer mask (more of the latter later). It works exactly the same as other selection tools such as the Magic Wand tool or the Quick Selection tool that you might be more familiar with.

That wasn't too complicated, was it?

Now, let's take it a step further...

The difference between luminosity masks and other conventional selection tools is that it creates selection based on the brightness value of the pixels. This means you don't need to physically draw the selection with your mouse cursor.

Don't worry if that didn't make sense. Let's try a different way of explaining things.

Luminance vs Hand Drawn Selection

Ordinarily, to create a selection, you'll have to pick a selection tool from the menu. These allow you to draw a selection with a circle, square, free-hand, etc. The selection is created based on where you click with your mouse cursor.

With luminosity masks, you don't have to draw the selection manually. The "action" analyzes the brightness of every pixels in the image and automatically creates a set of what is known as brights, midtones and darks luminosity masks. All you have to do now is to choose from a selection of masks you have created and use that as a selection.

Understand better now? Let's take a closer look at brightness and pixels!

Luminance of The Pixels

Brightness, lightness or luminance, it all means the same thing. The level of brightness is defined by the amount of black or white added to a color.

luminance or brightness

Pixels, on the other hand, are the building blocks of a rasterized image (JPEG, TIFF, Raw image, etc. are all rasterized image).

To visualize pixels yourself, open an image in Photoshop. Select the Zoom tool and zoom in to the maximum until you see multiple square boxes.

Each square is a single pixel!

It's actually very simple, right?

Selection Based On The Brightness of The Pixels

Now that you're clear about luminance and pixels, the rest is fairly straight forward!

Luminosity masks create selections based on the brightness of the pixels. There are three types of masks:

Brights, darks and midtones luminosity masks.

Using these masks, you can target select parts of the image with a single or a combination of luminosity masks. 

For example, if you want to reduce the brightness of the sky without affecting other parts of your image, use a brights mask targeting the sky (because the sky is bright in the image) and apply a tonal adjustment layer to it.

brights luminosity mask

Luminosity mask (right) targeting the bright pixels, which is the sky in this case.

That's all it is to luminosity masks!

So far so good?

Now let's make it more visual.

Why Gradient Map?

I found the black and white gradient map intuitive when it comes to demonstrating how luminosity masks work.

It will helps you to visualize what we've talked about so far - luminance of the pixels and creating selections based on that.

I encourage you to experiment with luminosity masks on the gradient map. Add, subtract and intersect the masks to see how it changes. Below are the keyboard shortcuts you need.

Keyboard Shortcuts To Select Luminosity Masks:

Cmd / Ctrl + left click = Select a mask
Cmd / Ctrl + Shift + left click = Add a mask
Cmd / Ctrl + Opt / Alt + left click = Subtract a mask
Cmd / Ctrl + Opt / Alt + Shift + left click = Intersect masks


Remember The Rules of Layer Masks:

Black conceals, white reveals and grey partially conceals/reveals depending if it's closer to black or white.

*luminosity masks = layer mask. You'll see how both relate later below*

Luminosity Masks And The Gradient Map

gradient map

The black and white gradient map is fairly easy to understand.

It starts with pure black on one end with a gradual transition to pure white on the other.

Intuitively, white has the highest luminance and black has none. This makes the middle 50% luminance.

You can create your own gradient map or download this PSD file which contains the gradient map above and all 18 luminosity masks in the Channels panel. Alternatively, create your own gradient map in Photoshop and generate luminosity masks with this Luminosity Mask Photoshop Action.

The Anatomy of A Luminosity Mask

the anatomy of a luminosity mask

When you click on a luminosity mask, marching ants will appear around the selection.

The area within the marching ants (the selected areas) will appear white on the layer mask. This means parts of the image covered by the mask will be revealed.

Conversely, the area outside the selection is unselected. This means it will appear black on the layer mask and parts of the image covered by it will be concealed.

The lines formed by the marching ants are not the border of the selection but the midpoint of the feathering transition. So, don't be fooled by the marching ants thinking that's the area being selected - the actual selection is always beyond where the lines are!

The Bright Masks

brights darks midtones gradient luminosity masks

Go to the Channels Panel to find the three groups of masks: brights, darks and midtones. Go through the masks in each group and the area the masks reveal and conceal.

Let's start with the brights mask. Brights 1 has almost half of the gradient map selected (the area in white). It feathers into the black (which conceals) in a smooth transition.

As you move from Brights 1 to Brights 6, you'll notice the area being revealed becomes less and the area being concealed becomes more. If you pay closer attention, you'll also notice that Bright 6 has the whitest of the whites. This means the selection is on the brightest area of the image.

To summarize, Brights masks select the bright areas of the image with Brights 1 selecting all the brights and Brights 6 selecting only the brightest. Brights 2-5 fall into the transition between Brights 1 and 6.

Now look at the darks masks. It's basically the reverse of the brights masks.

The Dark Masks

Similar to the brights masks but in reverse. Darks masks select the dark areas of the image. As you move through each mask, the area being selected becomes more restrictive.

When you move from Darks 1 to Darks 6, you'll notice the area being revealed (white) becomes less and the area being concealed (black) becomes more. You'll also notice that Darks 6 has the whitest of the whites. Because it's a dark masks, this means the selection is on the darkest area of the image.

So, to summarize, Darks masks select the dark areas of the image with Darks 1 selecting all the darks and Brights 6 selecting only the darkest. Brights 2-5 fall into the transition between Darks 1 and 6.

 I hope that makes sense!

The Unique Midtones Masks

The midtones masks are a bit different. As the name implies - midtones. It's in the middle of the gradient map.

But here's what's interesting.

As opposed to the brights and the darks masks, the area being revealed becomes more as you move from Midtones 1 to Midtones 6.

midtones 1 luminosity mask

Midtones 1 mask

Midtones masks can be challenging to understand. The best way I found is to visualize using the gradient map!

Scroll up to the collection of brights, darks and midtones masks above. In the first row, you'll see Brights 1, Darks 1 and Midtones 1. Midtones 1 is essentially the area that isn't covered by white in both Brights 1 and Darks 1!

As you move from Midtones 1 to Midtones 6, the area being selected becomes wider. All of these correspond to the areas not being selected by the respective brights and darks masks.

To summarize, the area being selected by Midtones masks increases from Midtones 1 to Midtones 6.

Luminosity Masks Through Visualisation

The easiest way I found to understand luminosity masks so far is to experiment with it and visualize the result with the gradient map.

To begin with, select Brights 1 mask and see the area it selects. Note how half of the gradient map is selected. Work your way to Brights 6 mask and you should see the selection gets narrower until only the brightest of the brights are selected.

Do the same for the darks and the midtones masks. It will give you an instant visualization on the selection of each mask.

Luminosity Masks = Layer Masks

Now that you understand brights, midtones and darks luminosity masks. What's next?

Once you've created the selection, apply it to an adjustment layer. Once you have done that, luminosity masks is applied as a layer mask to that layer.

luminosity mask and layer mask

So, essentially, luminosity masks is a layer mask.

Don't get confused with the terminology, both mean the same thing!

Conclusion

Luminosity masks is not rocket science but it does require a bit of imagination and time to digest.

The easiest way I found is to use the gradient map and play around with the masks to visualize the results.

Once you know how brights, darks and midtones masks work on the gradient map, take the next step by experimenting with one of your images. Remember, luminosity masks works the same as a selection tool on layer mask.

Ready for more?

Check out the Kickstarter's Guide To Luminosity Masks where we dive deeper into its application and pitfalls. I also have a free Photoshop Video Library where I walk you through Photoshop and luminosity masks.



  • David says:

    Wow!
    You have the best Luminosity Masks Tutorials out there.
    Really amazing stuff.

    Could you add reviews?
    Like reviewing Tony Kuyper Infinity Mask and NBP Lumizone?

    Thank You.

    • Yaopey says:

      Thanks, David! I had the idea of writing a review post on all the luminosity mask panels, then I came across this review article which has done a pretty good job. However, it didn’t include NBP Lumizone. Still, I think it’s worth checking out.

  • Richard says:

    Yaopey,
    Your tutorials are well written,explicit and a joy to read.I too was “in love” with HDR software for a number of years. Many thanks to you for your time and effort you put into your site. The fact that you offer so much at
    no charge speaks volumes.
    Thank you,,
    Richard

    • Yaopey says:

      Thanks, Richard! I knew I wasn’t the only one who went down the hdr hole. Just putting content out there so someone who is in where I was before can benefit from it! I’m glad you can resonate with my story!

  • Great tutorial, very clear and ordered. Beginner question: how do I apply the mask to an adjustment layer?

    • Yaopey says:

      Thanks for your comment, Michael. The easiest way you can apply a mask is by first selecting a luminosity mask from the Channels Panel. To select, cmd/ctrl + left click on the mask that you want. Then, select an adjustment layer and the mask will automatically load onto its layer mask.