Open the Photo Booth app
Click the red camera button to take a photo
Use the front camera if available
Open FaceTime or another video app and use its photo option if needed
Press Shift + Command + 3 to take a full-screen screenshot
Press Shift + Command + 4 to capture a selected area
Press Shift + Command + 5 to open screenshot controls
Use the Touch Bar camera button if your Mac has a Touch Bar
Connect an external camera and use it in a camera app
Save the photo from the app or screenshot toolbar