What is a layer mask?

Layer masks are an essential tool in Photoshop to create image manipulations. Among other uses, they allow you to ‘stack’ multiple images and expose only certain parts of the image/s above the base layer, creating a composite image.  You can do this using an eraser – but that is DESTRUCTIVE. If you remove something you wanted to keep, you have to go back to it before you erase that spot, possibly undoing other work.  Layer masks allow you to work NON DESTRUCTIVELY – if you remove something you wanted to keep, it’s super easy to get it back, and you don’t lose your work.

Lets Get Started

We’re using images from our recent splash! workshops, and the first set is by Beck Faldon

Step by Step

The goal is to combine all three, so we have the iceblock and both splashes in one image.  Hence the magic of layer masks.

• Open Photoshop and go to File>Scripts> Load files into stack.  From the little window that pops up, click ‘browse’, then find and select the images you want to use.  As the images I’m working with were taken on a tripod with virtually no difference between them, composition wise, I am also going to place a tick in the box ‘attempt to automatically align source images.  Then click ok. 
• Photoshop will now open all files, and if you click on your layers tab you will see they are all there, one on top of each other. You will also see that each layer has an eyeball beside it.. when the eyeball is visible that layer is visible, if you click the eyeball it turns that layer off.  Its still there, but no longer visible.

• Click the eyeball on the top layer and turn it off for now.  We are going to work on the second layer first up. To add the layer mask, click on the second layer (the middle one) so it’s active, then look to the bottom of the layers tab. 
• Click on the white rectangle with a black circle in the middle. It looks like the Japanese flag.  You will now have a white rectangle beside your second layer.  It’s important to remember that you must be doing it on the mask, not the image when you are painting.  See below the white bounding box around the white mask that shows me I am painting on that.  If you are painting and it starts turning black or white, you are painting directly on the image. 
• Go back a few steps until you have undone that, click on the white mask to make the mask active and start again. 

To Conceal or reveal

The key to layers masks is remembering that white reveals black conceals.  The layer mask is white. So you need to paint with black. Choose your brush tool, select 0% hardness, then click the black palette at the bottom of your main toolbar on the left.  Clicking the little double-sided arrow above your black and white palettes will toggle between black and white. You see 100% opacity on the image above, bring it down to about 70%, and see the layer below – it will help you choose what to reveal.

When you are finished, bring the opacity back up to 100%. As you paint, the mask will start to show black areas, where you painted concealing the top layer and revealing the layer below. Make your brush smaller and change it to a 100% hard brush to get into tight spots. If you take off parts of the image you want to keep, go back to your palette and click on the white palette to swap to a white brush. Now paint back the area you lost.  All the images were taken on a tripod, and there are no differences except the cup. I am painting the splash above the cut to combine the splash from both images into one.

Masking

You can now see that there is black on your layer mask.  There is where I brushed over the cup. The black area of the second layer is now hidden where it’s black, revealing the splash below.  Now we want to bring the ice cube into the pic.  Turn the top layer back on by clicking the empty box on the layer (where the eyeball isn’t), and the eyeball will come back as the layer is now turned on.  Don’t panic when you see that you’ve lost the splash. It’s all still there, just hidden below.  Click the top layer to activate it, then click the ‘Add layer mask’ icon again (the Japanese flag).  You will have another white rectangle now, just like the second layer.

Almost there

The area we want to expose now is the entire cup, keeping the falling IceCube above.  Select the black brush again and paint over the cup to reveal the splash but keep the ice cube. Likewise, just change to a white brush and paint it back if you make a mistake. Once you have finished, go to layer>Flatten image and edit in your usual way.  In the case of this one, I cropped and cloned out the inside of the bag you could see in the sack. (it was there to puff the sack up and make it look fuller).  I also added a subtle vignette.  

Some More Examples

Layer masks have many uses; if you are into family portraits and shoot them on a tripod, you can layer the images and remove heads cause it’s a battle to get everyone looking at the camera, eyes open, smiling. Layer the images, and you can brush out the ‘offending’ head.  I hope you found this helpful. Feel free to leave a like or comment 🙂