Luminosity masks are a great way to help enhance shadows in your images for more detail. While it would seem intuitive to use a darks mask to target and lighten your shadows, it often isn’t that straight-forward. Using a simple darks mask like D3 can often result in muddy shadows that lack contrast.
The underlying problem is that when you lighten your image through a darks mask, you are lifting near blacks faster than other dark midtones. That creates a loss of contrast and leaves the shadows looking flat.
There are a few ways you can address the issue, but one of the easiest is to subtract a more restrictive darks mask from your initial dark mask. For example, you can subtract D6 from that D3 mask. The result is similar to a D3 mask, but near black tones are protected (removed from the mask). This allows you to lift the shadows, while retaining true black for a better result with similar or enhanced contrast. Watch the following video for a demonstration to see how to create subtracted masks.
In addition using the subtract feature in Lumenzia to create better shadow adjustments, you can also use it to reduce the size of your files. Simply lasso areas of the mask that you will definitely not use, then click “-” and “Mask”. This will remove that detail from the mask, which can substantially shrink the size of your files (an estimated 30MB in the demo above).
To create a subtracted mask in Lumenzia in Photoshop CC:
- Create your initial mask (such as by clicking D4 and then the Levels icon to create a Levels adjustment with a normal D4 mask).
- Create a preview of the mask you wish to subtract, such as D6. You may optionally customize the orange preview layers as desired for even more control.
- Click on the layer with the initial mask (this tells Lumenzia which mask you wish to adjust, and you won’t be able to click on the “-” icon if you don’t have a valid target to adjust).
- Click “Mask” to complete the subtraction.
If you are using Photoshop CS6
- See this older version of this demo (as your workflow is slightly different). The general workflow illustrated by the buttons in the older versions of Lumenzia for CC illustrate how the process works in CS6.
- Create your initial mask
- Create the preview or selection you wish to subtract.
- Click the “-” button next to the “Mask” button. The subtraction occurs immediately in CS6.
If you are using my free luminosity masking panel:
- Create the luminosity masking channels
- <ctrl/cmd>-click one of the channels to load it as a selection
- <alt/option><ctrl/cmd>-click the channel to be subtracted (note that in recent versions of Photoshop the cursor will show a tiny “-” while you hold these keys and hover over channels). This gives you a subtracted luminosity selection.
- Create a new layer or add a layer mask to an existing layer. This will convert the subtracted luminosity selection into your subtracted luminosity mask.