Post-Processing » Photoshop Tutorials » Introduction To Luminosity Masks in Photoshop

Introduction To Luminosity Masks in Photoshop

Luminosity Masks are one of the most popular techniques of editing in Photoshop. They are used by all those photographers who want to go deeper than the commonly used adjustments in Photoshop. Luminosity masks are largely used by photographers who want a clean, natural, and vibrant result, without using other software or filters to reach the desired effect.

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What are Luminosity Masks?

Luminosity masks are an advanced selection method, based on specific tonal values in the image.

image edited using luminosity masks

There are three types of luminosity masks used in order to create and refine the selection from the brightest to the darkest areas of the image. The three types of luminosity masks covers:

  • Highlights
  • Shadows
  • Midtones

Each of them is created a little bit differently in Photoshop. 

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To learn using luminosity masks, you should first know the basics of Photoshop. Furthermore, as said above, it is workflow dedicated to all those photographers who want to go more in-depth than the traditional use of Photoshop.

Using luminosity masks allows you to have control of the exposure blending process. To master using luminosity masks, you should know the basics editing of Photoshop and clearly understand the use of layer masks, levels, and channels. Once you know how to use these features in Photoshop, you will be ready to look at the more advanced technique of using luminosity masks.

Learning to manually blend several exposures using luminosity masks can take your post-processing to a whole new level compared to using automated HDR software, that often results in surreal and oversaturated photos.

After many years of Photoshop, I use luminosity masks in all my images, especially when combining multiple exposures and digital blending.

Here I decreased the sky highlights to recover sky colours

How to Create Luminosity Masks in Photoshop

In the following steps, we will see how to create luminosity masks. In the beginning, it can be a little confusing, but soon you will realize that it is a simple procedure to do through channels.

To create luminosity masks let’s start with creating the highlights selection.

Creating Highlight Selection Mask

Once you’ve opened an image in Photoshop, follow these steps:

  • CTRL + Click the RGB thumbnail in the Channel Tab
  • Save the selection
  • You will have “Alpha 1” channel
  • Rename it to “Highlights”, or “Lights”
  • CTRL + D to deselect the selection
luminosity masks channels

This is your first Luminosity Mask! Here is what happened:
Luminosity Masks are selections based on the brightness of the image. When you select the RGB channel, a selection with marching ants will appear. Once you save this selection, it will represent the broader highlights (commonly renamed as Highlights or if you prefer Highlights 1 or Lights 1)

Creating More Specific Luminosity Masks

The selection we made in the steps above is the broadest selection of highlights. Working with luminosity masks allow us to refine and create more specific selections.

To further refine the Highlights selection, you need to:

  • Select the Highlights 1 channel by CTRL + click on the thumbnail
  • With the marching ants active, SHIFT+ALT+CTRL + click on the same thumbnail
  • Save the new selection and rename it to Highlights 2
  • CTRL + D to deselect the selection

This second selection represents a more specific one, that is, a more narrow selection of highlights than those created in the previous steps. You can go further refine these masks repeating the same process to create Highlights 3-4-5-6 or as many as you will need for your image.

Creating Shadows Selections

Once your are finished with creating the Highlights masks you need, it’s time to create the Shadows/Darks masks. To create this kind of masks we need to repeat the same process but inverting the selection.

  • CTRL + Click the RGB thumbnail in the Channel Tab
  • CTRL+SHIFT+I to inverse the selection
  • Save the selection
  • Double Click the new channel and rename it to “Shadows” or “Darks”
  • CTRL + D to deselect the selection

Also here you can refine the selection following the same steps done for the Highlights channels, but without inverting the masks because you will use Shadows 1 as the source, which is already inverted.

Creating Midtones Selections

Creating the Midtones masks is a little bit different than creating Highlights and Shadows. The creation of the midtones masks is based from the selection of the highlight and shadow masks we just created.

To create the Midtone Masks:

  • Press CTRL + A to select the entire image
  • Subtract Highlights by pressing CTRL + ALT + click on the channel’s thumbnail.
  • Subtract Shadows by pressing CTRL + ALT + click on the channel’s thumbnail.
  • Save and rename the new selection as Midtones 1
  • CTRL + D to deselect the selection

To create a refined selection you will need to:

  • Press CTRL-A to select the entire image
  • Subtract Highlights 2 by CTRL + ALT + click on the channel’s thumbnail.
  • Subtract Shadows 2 by CTRL + ALT + click on the channel’s thumbnail.
  • Save and rename the new channel to Midtones 2
  • Ctrl+D to deselect the selection

Continue the steps above until you’ve created all the midtones selections you desire.

Luminosity Masks main applications

Once you have created the set of luminosity masks, you can use these advanced tonal value selections for further editing and blending.

Every time you will select a luminosity mask, the marching ants will show you which part of the image is affected.

Luminosity masks can have multiple different uses. Let’s start with using them for something easy.

In the following image we need only to affect the highlights, with the curve adjustment layer to darken the sky. Without a luminosity mask the sky might look better but some darker areas of the foreground will become too dark, and this will compromise the final result.

non-edited image

As you can see below the sky looks good but the rest of the image is much too dark

Image edited with Curves without Luminosity Masks

Now let’s see create the same curves adjustment layer applied, but using to luminosity masks to limit the affected area:

  • Go to Channels and press CTRL+click on Highlights
  • Go back to Layers and launch curves adjustment layer
  • The curves adjustment layer now only affects what is inside the Highlights selection
  • Decrease the curve to darken the highlights
Image edited with Luminosity Masks applied to Highlights

By using luminosity masks, we only affected the sky and those parts of the frame we needed. You can select more specific highlights (like Highlights 2 or 3) for more accurate selections.

Using the same curve adjustment layer tool, we can do the same to increase the shadows and make the rock look less dark. We can do the same process done before using darks

  • Go to Channels and press Ctrl+click on Darks (1)
  • Go back to Layers and launch curves adjustment layer
  • The curves adjustment layer is now limited to affecting what is inside the dark selection
  • Increase the curve to lighten the darks
Image edited with Luminosity Masks applied to Highlights and Shadows

Every selection affects the image differently.

In general, consider that highlights, darks, and mid-tones selection start from the largest till the smallest selection. I.e., using Highlights 1 will give you a wider selection of highlights compared to Highlights 3 or 4.

Making adjustments through luminosity masks allows you to target a specific area of an image. It would be hard to get acceptable results without affecting the whole image if you didn’t apply luminosity masks for this.

Keep Experimenting

We’ve seen just one example of the possible adjustments we can achieve through luminosity masks, curves, and layers are only an example of the possibilities. There are several other examples of the adjustments you can use.

Some of the most used are: curves, color range, hue/saturation, photo filters, levels, brighten and contrast and all other photoshop adjustment layers.

Blending multiple images

Digital exposure blending is one of my favourite use of luminosity masks. This technique is commonly used to blend bracketed shots in order to take the best selection of the highlights and shadows. Taking multiple exposures allows you to capture all the dynamic range of the scene and use the exposures you need to blend into the final image

Importing all the exposures you need and place them on top of each each other, you will be able to create a precise mask by manually using a brush combined with luminosity masks, to the layers below visible.

Luminosity masks are extremely useful in situations like this. The mask will target only specific values of the image, so you are now able to blend the brighter exposure into only the areas which are underexposed and vice-versa.

Download Luminosity Mask Actions for free

To easily create luminosity masks, I created a free panel to download.

By following this link you can download a free photoshop extension that will allow you to easily create and delete all the luminosity masks set (with the possibility to generate only lights, darks and midtones stand alone).

Furthermore the panel contains some other effects that you can use with your luminosity masks to improve your images.

For those who need a more advanced and specific method on luminosity masks and digital blending, I created a complete course that will leads you to mastering this technique.

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