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

This is about frame48, and Mary is still not turned towards the Kennedys. She is looking straight ahead; facing straight ahead. 

So, what are we to assume? That she did turn for an instant to take their picture and then turned back? In a split second? 

This is the very last time that we see Mary with her camera raised to her eye in picture-taking mode in the Muchmore film.

After that, she puts her camera down, and she never raises it again. Notice that the Kennedys have not passed her yet. Notice that neither Hargis nor Martin have reached her yet. And notice that shooting at that moment would have put the Kennedys in the center of her picture, with no problem. So, that is the last time Mary was in picture-taking mode, and she could not possibly have captured the Moorman photo at that moment.