A few days ago we covered the types of layers and I mentioned that adjustment layers come with masks and we can add masks to duplicate and blank layers. I am sure some were wondering, what the heck is a mask though?
A mask is a tool of sorts, which allows you to hide (or “mask”) some of the changes on a layer. For instance, if you make an adjustment and you love what it does to most of the image, but not all of it, you can use the mask to get rid (or brush off) the change on parts of the picture.
This is something best taught by example, so let’s get to it….
Below is an image that I’m going to edit with a few layers and I will make use of the masks that come with the layer, or I will apply one on my own.
Step 1: Create a Levels adjustment and pull in the black slider a good bit, to meet the base of the histogram “mountain.”
Step 2: This change made her face quite dark, so I am going to brush off some of it with a black brush. Click your brush tool and make sure the top color in the bottom boxes is black (hit ‘d’ on keyboard if they are other colors).
What the mask looked like after I brushed over her face to hide the change in that area.
Step 3: Created a Levels adjustment to bright and warm her face a bit. I didn’t want this change everywhere, so after making the adjustment, I pressed ‘control’ and ‘i’ to invert the mask from white to black (‘command’ and ‘i’ on a Mac). So now the change is being hidden under the black mask and the only way to see any of the change is to brush on the image with a white brush.
(For the record, the change I made was not the best way to do it, I kept it in one layer to keep it simple for beginners reading)
Step 4: Change your brush from black to white by pressing ‘x’ on your keyboard. Below shows you that white should be the top color in the color boxes at the bottom of your tools. Brush over the area you want to show or bring out the change.
What the mask looked like after I brushed only over her face:
Now, when using a brush, you need to make sure it is soft (see the stroke in green below – it has a halo around it) and that the brush opacity is high enough to show or hide the change. I don’t recommend using 100% opacity brush.
I made two more adjustments, a soft light pop which I did not brush off and a Hue/Saturation adjustment which I inverted and only brushed on the whites of the eyes (sorry it says teeth, I’m tired this morning and too lazy to change it).
If you run an action and it has a black mask, that means there is a change hiding under there and you have to reveal it with a white brush. Below I ran the free skin smoothing action I have and will use a white brush to bring out the change only over her face.
Here is the before and after comparison. Small changes, but makes a difference.
As usual, I did a quick video tutorial to walk you though the steps above. I hope this helps you to understand how and why to use masks.