Photoshop Tutorials: Making Your Subject Pop Out Of A Photo
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Step 4: Select The Object(s) In The Photo You Want To Have Pop Out
Click back on "Layer 1" in the Layers palette to select it. Then, using the selection tool of your choice, make a selection around the object(s) you want to have popping out of your photo.
In my case, I want the football player in the center of the image, as well as the player in red directly behind him, to pop out, so I'll use the Pen Tool to select them. You can use the Pen tool, the Lasso tool, or whichever selection tool you prefer:

Step 5: Copy The Selection To A New Layer
Once you've made your selection, with "Layer 1" selected in the Layers palette, press Ctrl+J (Win) / Command+J (Mac) to copy the selection onto a new layer. Again, you won't see anything happening in the Document Window, but you'll see your selection copied to a new layer at the top of the Layers palette:

Step 6: Drag A Selection Around The Rest Of The Photo You Want To Keep
Click back on "Layer 1" in the Layers palette to select it. Then press M on your keyboard to quickly select the Rectangular Marquee Tool and drag a selection around the rest of the photo that you want to keep, essentially creating a smaller, cropped version of the image. Make sure you select an area small enough so that some of the object(s) you selected a moment ago will stick out, which is what's going to create our "popping out" effect:

Step 7: Add A Layer Mask
Once you've dragged out your selection, click on the Add A Layer Mask icon at the bottom of the Layers palette:

This will add a layer mask to "Layer 1", and because we had part of the layer selected, only the area inside the selection will remain visible. The rest of the photo that fell outside of the selection will now be hidden from view:

We can now see the "popping out" effect taking shape.