The mask Density slider has been around in Photoshop for a long time, it can be very useful, but a lot of people don’t understand what it does, or how it can be used.
Before we talk about it in more detail, let’s do some basic revision on what Layer Masks are and what they do.
Every layer, whether it be a pixel-based layer or an Adjustment or Fill layer, can have a layer mask.
You can paint on the layer mask in black or white (or any shade of grey) and wherever the layer mask is black the pixels on that layer, or the effect of that layer (in the case of Adjustment or Fill Layers) will be blocked.
Wherever the layer mask is white, the pixels on that layer (or the effect of that layer) will be complete (100%).
For shades of grey the pixels or effect of that layer will be partially “blocked” depending upon the darkness of the shade of grey.
“Black conceals and White reveals” is a saying often used to remember the effect of a layer mask.
You can paint on a layer mask in many ways, but the tools most often used are the Brush tool and the Gradient tool.
If you have a selection active when you create a mask that selection will be used to create the mask, so a common way to create a mask is to use a selection technique (Select Subject, Select Sky, Object Selection Tool) first, then the layer mask will be created with white for the selected parts and black for the unselected parts.
Using a layer mask is a preferred method of operating as it is non-destructive. That is, it doesn’t destroy or alter any of the pixels in your actual image.
When you have a mask selected, the mask properties will be shown in the Properties panel (choose Window / Properties if the Properties panel is not visible). The Density slider can be found here (see Figure 1).
Figure 1 - Mask Properties panel
The mask Density slider affects the non-white (black or shades of grey) parts of your mask, white parts of the mask are unaffected by the Density slider.
The mask Density slider defaults to 100% (fully slid to the right) where it leaves the mask exactly as you created it.
As you slide the Density slider to the left the blacks and greys in the mask get gradually lighter (or more transparent), until at 0% the whole mask will be white, letting the pixels or effect of the layer show through completely in your image.
Let’s look at an example.
Let’s look at an example.
In Figure 2a, I have an image of an Eastern Yellow Robin. I have run the Nik Color Efex filter and used the Pro Contrast preset to increase the Dynamic Contrast in the image. I have then used Select Subject to select the bird and the branch and created a layer mask. This “protects” the background from the contrast adjustment and means it is only applied to the bird (through the white parts of the mask).
Fig 2a - Mask Density example
Now, if I decide I would like to allow some of the increase in contrast to apply to the background, but not at full strength, I can slide the Density slider to the left. The black in the mask that is protecting the background will get progressively lighter, allowing some of the contrast adjustment through to affect the background. In Figure 2b the Density slider is at 50%, so the mask on the background is 50% grey allowing the contrast adjustment to affect the background at half strength.
Fig 2b - Mask Density example
Another adjustment where the Density slider is useful is when applying noise reduction. Often noise is much more noticeable in areas of low contrast (like the sky or a blurry background) and is less noticeable where there is finer detail (eg in my bird and branch).
In addition, if you apply a strong noise adjustment it will work well on a sky or blurry background but will often destroy the detail in other parts of your image.
So, in Figure 2c I have created a new layer and applied some noise reduction. I have duplicated the mask from the previous layer and inverted it (by selecting it and pressing [Cmd/Ctrl+I]). Then I have moved the Density slider to about 60% which allows me to use a reduced amount (40%) of noise reduction to my detail areas and full noise reduction to the background.
Fig 2c - Mask Density example
Another good use of the Density slider is when using gradients on masks. In the example shown in Figure 2d I have used the Nik Color Efex Detail Extractor preset to pull some detail from shadows, and added an orange Solid Colour layer, set to Soft Light, to add some light and colour. I have grouped these two adjustments and added a mask on the group, then used the Radial Gradient to limit the adjustments to the centre of the image, radiating out from the sunrise.
Then, deciding I’d like some of these adjustments across the whole image, I moved the mask Density slider to 45% allowing a little more than half-strength adjustments across the whole image.
Fig 2d - Mask Density example
Another use for the mask Density is when you are painting into a black mask to reveal objects or adjustments. A temporary change to the mask Density (perhaps to 50% or something) can help you “see through” the black mask while painting through it.
So, if the mask Density slider is something you’re not familiar with, or not using much, I encourage you to try it, then I’m sure, like me, you will begin using it more and more.
This article was first published in the June 2024 issue of Artists Down Under magazine.