Photo Booth snapshots have the same orientation as the image in the live video view, but this might seem backward when you’re looking at the picture. You can flip a picture you’ve taken so that it’s oriented the right way for you.
To flip a snapshot:
At the bottom of the window, select the thumbnail of the snapshot you want to flip.
Choose Edit > Flip Photo.
To flip snapshots automatically when you take them:
Choose Edit > Auto Flip New Photos.