Masking in Photoshop CS4

The Basics of creating a mask

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If you’d like to define your subject and create a different background, this tutorial is the one for you.

When I play with Photoshop, it’s basically just to make pictures look better, or funny, or something. So if that’s your goal with this software, then read on, my friend.

I’m just going to use a couple images from the internet, as examples. My subject is going to be a running dog, and place it in a different background, next to some racing greyhounds.

So once you have Photoshop CS4 opened up, find the image you want to use by clicking File > Open, and locating your file, or by clicking the “bridge button”


and locating your file from there.

Once you have your desired image, find the “Quick Mask” tool on the very bottom of your toolbar on the left-hand side

Make sure you have your paintbrush tool selected, and make your brush size bigger, so it’s easier to get the full subject in, and it’s less time consuming
When you have all of your subject selected, it will have a red mask on top of it that looks like this:

Click the “Quick Mask” button again, and you should end up with a dotted line around your subject, and the outline of the picture.
On the right-hand side of the screen, select your “Masks” tab

and next to where it says “No mask selected,” you’ll see 2 icons, you want to click the first one, that looks like this:

Now your picture will have the background of your image, with the checkerboard subject that you want. Next you need to click the “Invert” button, that’s located in the same Masks tab, just at the very bottom, it looks like this:


Clicking the button will obviously invert your picture, and make it so the subject is visible, and the background is checkered.

So your subject probably still has some background that you don’t want in there, what you need to do next is select the “Quick Selection” tool.
(note: you can use whichever brush you want, if you use a paintbrush to be more precise about what is being selected, black will take out the color- in case you need to take out more background- and white will add color- to add more if you accidentally deleted too much.)
but the “Quick Selection” tool and the “Magic Wand” tool that is hidden under the quick selection tool will be your best choices. They look like this:

Zoom in on your subject, with the “Quick Selection” tool selected, and start to click around the edges of your subject, deleting the excess background that you don’t want in your finished picture.

If you end up getting to a point where your selection tool selects into parts of your subject over and over, no matter what, you can get more precise with the “Paint Brush” tool, which you will have to have set as black, which will delete the color that you want deleted.


As you can see with my subject, the grass from the background stayed around the back right leg, so I went in with the paint brush to take out what I didn’t want in there.
I also took out some of the grass from between the hairs that the “Quick Selection” tool or the “Magic Wand” tool couldn’t pick up.

When your mask is complete, the layer in the “Layer Panel” should look similar to this:

(NOTE: BE SURE TO SAVE FREQUENTLY!!!)

After you get your subject looking how you want it, open up your desired background image using the same method you used to get your subject image.

When you’ve found your background image, and you have it opened, it will come up in a new window. To add both layers together, click the “Arrange Documents” button in the top tool bar:


The drop down box will lead you to:

You want to click the “2 Up” option that looks like:

Now both of your images will be displayed right next to each other. The easiest way to do this, is to drag your subject onto your background, so you don’t have to go through the trouble of re-arranging the layers. Make sure your “Move” tool is selected, click and drag your subject image to your background image, and the subject will show up among your background.

Now, I will want to re-arrange where I want my dog on the background, and I will re-size it, too. If you want to re-size it, make sure that your dog layer is selected, go up to Edit > Free Transform, and you will then be able to re-size. To make sure my dog’s body stays proportional, I will click one of the corner edges and hold down the Shift key (note: make sure you hold the Shift key down until you’re done dragging.)

The good thing about Free Transforming, is that you can move your subject while the transform is taking place.

When your subject is where you want it, and the right size, click the “Commit Transform” button to save your changes


If you end up not liking the transform, and want to start over, or just don’t want to change anything, click the “Cancel Transform” button located right next to the “Commit Transform” button.

My white dog is a little bit more clear than the greyhounds, but that’s easily fixable. Click and hold the “Blur” tool, and within the selection is the “Sharpen” tool.

Select “Sharpen” tool, and select the layer that needs to be sharpened, in my case the background. Make your brush size to its largest, by going up to the top, selecting the drop down box for “Brush” and moving the scroll bar to the very right, so the brush affects the whole picture.

Once you double check that the correct layer is selected, and that the brush is large enough to cover the whole screen (note: if it is, the brush icon will be a little plus sign instead of a circle), click over the image until it is at the desired sharpness.
I decided to click twice for the background, and once for the subject, just to make it a little more even.

If everything looks how you want it, save your work as a name other than your background layer- because your other image was added to the background- and show off to your friends how awesome your photo editing skills are. 🙂

Thanks for reading!


^the finished product^


image of dog 1 found at http://www.hot-screensaver.com/2007/05/21/very-cute-puppies/
image of greyhounds found at http://soapboxprincess-ellie.blogspot.com/2008/04/beauty-in-motion.html