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

It's important to remember that the professor figured this out without any explanation from me. I didn't give him any pretext whatsoever. I didn't want to bias him. I just asked him to look at the photo and determine where the photographer was in relation to the objects in the picture. 

He came up with this just from looking at it:

And I can tell you that it's because the line of the car is not parallel with the bottom of the picture that gives it away that the picture was taken on a diagonal. The fact that the subjects (the Kennedys) aren't centered is another tell-tale sign. If the picture was taken squarely (from a perpendicular angle) it would have been very easy to center the subjects, as people do all the time.