Oswald in the doorway: the blog of the Oswald Innocence Campaign, by Ralph Cinque

People are not invisible or transparent, and no parts of them are invisible or transparent. 

When you see them, you see the parts of them that are closest to you, that are first in your field of vision. 

The close parts may block the visibility of the distant parts because they are in front of those distant parts. 

You can't see a distant part without seeing the closer parts when the closer parts are between you and the distant part.

 From this angle, you can this man's right arm, but you can also see his left arm, and you could not possibly see his right arm without seeing his left arm. And it's because his left arm is there- between you and his right arm. As you look at him, you see everything between you and his right arm, and that includes his left arm. And it is exactly the same way for a camera.