Learning Software (Version CS6 for Macintosh; see below for link to CC 2017 update)
A self-guided tutorial by Ross Collins, North Dakota State University
This is incredibly handy for magazine cover design, when you need a transparent background. And Photoshop gives you more than one way to do it, of course. Here are two methods.
You may wish to delete a background and replace it with nothing--that is, create a transparent background. Or you may wish to delete a background and fill it with something else. Both begin the same way.
You can do this exercise with your own photos, or choose these:
I. The background is nearly monochromatic.
If your background is pretty much the same color, and different from the foreground, you can just erase it.
1. Create a Duplicate of the background layer from the Layers pulldown or the flyout menu at right of Layers panel.
2. Turn off the original background layer from the Layers panel by toggling off the eye icon.
3. Choose the Background Eraser from the toolbox.
4. Set the tolerance in the contextual menu at top as necessary. Start with about 25 percent, Limits to Contiguous.
5. Set the cursor size as necessary (use the bracket keys as a shortcut, [ and ]) and click and/or drag to erase background. You may have to adjust cursor size and tolerance several times. Begin with a large size Background Eraser.
6. To repair areas of your image you want to keep, Choose the Eraser Tool. Toggle on Erase to History (opacity at 100%). Erase areas to bring back the image as necessary. Clean up background by dragging Background Eraser. (Use keystroke command to zoom in or out: Command and + or - keys.) Save as Photoshop to keep your layers, or as jpg to flatten.
7. You can replace a background, if you wish. Working from the photo above (with background copy layer), Open a second photo with a background you'd like to borrow. Copy the area on that photo that you want to be the background for the original photo.
8. Choose New Layer from Layer pulldown or panel flyout. Paste the image onto that new layer.
9. In the Layers panel drag the background copy layer up--this puts that layer above the other layer.
9. Scale the background image on that layer to fit by choosing Transform, and Scale from the Edit pulldown. (Alternatively you can scale your background layer the same way. Toggle off Visibility on background copy if necessary so you can see it.)
10. Working on the background copy layer, choose the Background Eraser tool and erase again, as you did in the exercise above. Use the Command-z keystroke to go back, if necessary. Yes, I know this takes a deft touch. Mousing precisely is a skill....
11. Save as jpg.
II. Background is cluttered.
It's sometimes harder to do a good job with the Background Eraser in a multi-colored background. So let's try a Quick Mask instead.
1. Open photo in Photoshop. Duplicate background layer, and work from background copy layer. Toggle off view of original background layer, as above.
2. Choose Edit in Quick Mask Mode from bottom of toolbox or from Select pulldown.
3. Choose the Brush Tool. Choose a hard edged brush, opacity 100%.
4. Brush in the image area you want to keep. Note it will change to a ruby red as it's masked. Try to do your best, but it doesn't have to be perfect.
5. Click off Quick Mask mode. The ruby area turns to a selection.
6. Adjust your selection more accurately using the Lasso Tool and + or - keys. The - key will select areas of the mask you want to add, or vice versa.
7. When you're ready, choose Delete. Deselect.
8. If you want to delete the foreground instead of the background, choose Inverse from the Select pulldown, and then Delete.
9. If you wish, add another background as explained above.
Assignment to submit for grading: Download the sample photos above, or choose your own. Erase or delete background as described above, replace with new background. Now that you've become a Photoshop exert, I will deduct points for sloppiness!
New! Alternative approach to deleting backgrounds in Photoshop CC 2017. See Select and Mask.