Begin with two images you want to combine, on separate layers, in Photoshop. (If you’re not sure how to get two images on separate layers, see this super-quick tutorial on Adding and arranging images).
In the Layers panel, click the eye icon next to the bottom layer to temporarily hide it. (If the panel is not visible, choose Windows > Layers).
A quick way to do this is by choosing Select > Select and Mask from the main menu.
Note: This is a new feature in Photoshop. Make sure you’ve updated to the latest version!
Use the Quick Select tool to paint over an area you want to isolate. On your own image, it could be a background or any other area you want to knock out and replace with the image beneath. If you select too much of the image, hold Alt (Windows) or Option (Mac OS) while painting to subtract parts from the selection.
Experiment with the Transparency slider, on the Properties panel that appears when you choose Select and Mask, to see the areas you selected versus the unselected areas.
By default, the area you paint over will be the part of the image that remains visible. If you want to hide that area instead, simply click Invert from the Select and Mask Properties panel. This creates a mask where the area you’ve selected becomes transparent.
Under Output Settings in the Properties panel, choose to output the selection to a Layer Mask. Click OK.
The new black and white thumbnail in the Layers panel is called a Layer Mask. Anything defined with black on the Layer Mask will be hidden to allow the image underneath to show through. Anything defined by the white area remains visible.
Click the eye icon to make the bottom layer visible. You should see part of the bottom image showing through the area you defined for the top image.
Once you see the bottom image revealed, you may see areas of the mask you want to edit. You can paint with black or white directly on layer masks to hide or reveal more of that layer. Choose the Brush tool and set the foreground color to black.
Click the Layer Mask in the Layers panel to select it. Now, paint with black on the image to hide more of the top layer. Or, paint with white to reveal more of the top layer. Choose a softer brush or lower the opacity to create a softer transition in some areas.
It’s okay if you make a mistake. Just press Control+Z (Windows) or Command+Z (Mac OS) to undo.
You’ve made it this far, and you’re doing great. Masking takes practice, but it’s a lot of fun to create composites. If you want a little more of a challenge, you can refine the mask further to create effects like the one here, where we revealed more detail of the surf extending beyond the pool edge. Here’s how we did it:
We selected the Brush tool, chose a textured brush in the options bar, and then lowered the brush’s opacity. We set the foreground color to white and selected the Layer Mask by clicking it in the Layers panel. We then painted with white on the Layer Mask to reveal parts of the top image.
Original surf photography from the making of View From A Blue Moon, one of the most ambitious action sports film projects to date. See more at viewfromabluemoon.com.