3 Effective Methods to Select and Apply Luminosity Masks

Luminosity Masks are considered an advanced technique but with a little bit of basic Photoshop knowledge, you’ll be surprised to see just how easy they are to create and apply to your images.

There are a few different ways to apply Luminosity Masks and while they are pretty straightforward, it’s important to learn which method to use in various situations.

#1 Applying the Full Mask From Selection

The first, and perhaps most common, method is to create an Adjustment Layer through a Luminosity Mask selection. It’s a standard way to use a Luminosity Mask with adjustments such as Curves, Levels and Color Balance.

1. Activate the Luminosity Mask you want to use (Ctrl/Cmd + click on the channel’s thumbnail) and the marching ants pop up
2. Create an adjustment layer and the selection is automatically applied as a mask

Let’s say that you want to darken the brightest areas of a sky by using a Curves adjustment layer and Brights 3 is the mask that best represents the areas we want to darken.

1. Ctrl/Cmd + click on the Brights 3 channel’s thumbnail to activate the selection. Marching ants should now be visible around the brightest areas of the image.
2. Create a curves adjustment layer.

Notice that the grayscale version of the image (representing Brights 3) is added as a Layer Mask. This means that adjustments made on this layer will only affect the non-black areas of the mask.

Recommended Reading: An Introduction to Luminosity Masks

#2 Adding the Selection to an Existing Layer

The second method of adding a Luminosity Mask is to apply the selection onto an existing layer. This is the more common method when working with layers that aren’t automatically given a layer mask (such as a Dodge & Burn or Merge Visible layers).

Let’s say you’ve created a Merge Visible layer that you want to apply a mask to. Go to the channels panel and activate the Luminosity Mask you want to use (for example, Darks 2). Next, go back to the Layers Panel and click on the merged layer. Click the Add Layer Mask… icon found below the layers to apply the mask. Clicking this icon will apply the Layer Mask to whichever layer you’re on.

Note: Clicking the Add Layer Mask icon without activating a selection beforehand would create a white Layer Mask.

#3 Painting Through a Luminosity Mask Selection

The final method we’ll look at is painting through a Luminosity Mask selection. This is a common practice when you’re Dodging & Burning or applying an effect to only specific areas of the image (i.e. not all the highlights or all the darks). Let’s say that we want to add blues into our foreground shadows. The Darks masks perfectly target all the shadows in the image but we only want to affect the foreground shadows so how would that work?

First of all, do not open a mask beforehand. Start by creating a new Adjustment Layer (I prefer the Color Balance Adjustment Layer when working with color) and make the adjustments you want. Since the Layer Mask is completely white, the adjustments you make will be applied to the entire image but we’ll change that. Since we want to affect only certain areas in the foreground, we invert the Layer Mask (select the mask; click Ctrl/Cmd + I) and it turns black, i.e. the Color Balance adjustment you made is no longer visible on the image.

Next, choose the Brush Tool and set the foreground color to white. Now activate the Darks 1 or whichever mask you want to use. The marching ants become visible, which tells us that the selection is active. (I hide the marching ants by clicking Ctrl/Cmd + H at this point) Finally, click on the black Layer Mask and start painting around the foreground with the white brush. Note that only the shadows that were selected in the Luminosity Mask are affected – the rest of the foreground content remains untouched. You can adjust the Layer- or Brush Opacity or modify the Color Balance settings if needed.

Note: You can also remove an adjustment from areas by using a black brush on a white mask, meaning that you didn’t need to first invert the mask. This is a good option when you want the effect to be applied to most of the image except for certain areas.