Masks are a very effective tool to do many things in Photoshop and can be extremely useful in your edits. The purpose of this tutorial is to give you a very brief understanding of how to use a mask to reveal or hide portions of an image by using layer masks. It is in no way a comprehensive study of masking, but will give you some basics for getting started. I urge you to explore this feature deeper.

For this tutorial, I chose two images. The first is the image taken indoors looking out a window. The second is an image of Mt. St. Helens. The goal is to change the first image so that the view out of the window is the second image.

First, open both images and make sure that they have similar properties. They should both be the same color space, similar size, and both the same bit depth (either 8 or 16). Once that is done, click the move tool (shown by the arrow in figure 1) and drag the image onto the other image.

Figure 1 - Click on image to see full picture

In my example, I dragged image 2 onto image 1, but it could have just as easily been done the other way. Figure 2 shows the new layer sitting on top of the background layer. Because I chose to use the indoor image as the background layer, I need to duplicate that layer. The quickest way to do this is to click the background layer in the layers palette, then press “CNTL J” on the PC or “Command J” on the Mac. This places a duplicate copy of the layer just above the background layer.

Figure 2 - Click on image to see full picture

Change the layer order by selecting the background copy in the layers palette and dragging it above the layer that contains the new scene (in this case, layer one). See figure 3.

Figure 3

Figure 4 shows how to add a mask layer. First select the layer you want to add the mask layer to, then click the icon at the bottom of the layers palette indicated by the arrow (1). The resulting masks is shown at arrow (2).

Figure 4

Now, we’re ready to start using the mask we just created. The key point to remember is that for your mask, black hides and white reveals. Notice that your mask in the layers palette is filled with white, meaning that everything is revealed. In the case here, this basically means that nothing is being altered by this mask yet. By painting on that mask with black, we will hide that information and in this case the lower layer will be revealed. Start by making sure your background and foreground are set to black and white. Press key “D” to set them to the default foreground/background colors. “X” will shift the background and foreground colors back and forth as desired. Select a hard edged brush, check that the opacity is set to 100%. Click on the layer mask in the layers palette before painting (if you are on the image itself, you will paint black on the image… not what we want to do here). Using your brush (you can quickly resize your brush using the [ or the ] keys), paint the area in the window. Note how the lower layer becomes visible.

Figure 5 - Click on image to see full picture

To continue with the project, you can use a variety of tools to obtain your objective. While you could easily just continue painting out the area desired, changing brush size and zooming in as needed, you can also use selections as I’ll show you using a simple rectangular marquis tool in the following examples.

Figure 6 - (arrow indicates selection) Click on image to see full picture

Select “Edit” > “Fill” (figure 7), then select black (figure, click “OK” to fill the selection with black (figure 9).

Figure 7

Figure 8 - Click on image to see full picture

Figure 9 - Click on image to see full picture

And my final result (including the man that I added afterwards) is shown below.

Figure 10 - Click on image to see full picture

One issue that I realized while writing this tutorial is that because of the way I set the layers, the “reveal” and “hide” issues appear backwards. This is because of the way I had my layers set up. In any case, I think you probably got the idea. One more tip… when you add a layer mask, it defaults to white. If you want to start off with a black layer mask, there are two ways to do this (I’m going to talk PC here… not sure how the Mac works on this issue). You can either hold down your “CTRL” key while clicking the layer mask icon and therefore generate a black layer mask or, if you’ve already created the layer mask, you could click on the layer mask in the layers palette, then press “ALT” + “Backspace” and the layer mask will fill with black.

I hope that you have found this short tutorial of benefit and that you’ll explore all of the possibilities that layer masks have to offer. Happy Photoshopping!