Were the photographs in the closing credits of "Rain Man" actually taken by Dustin Hoffman with the instamatic camera shown in the movie or were they actually shots taken by someone else with a good camera with the intent to make it look like they were shots taken during the movie?

You can't enlarge a picture taken with an instamatic camera to more than about 10 inches without it looking grainy. When expanded to the size of a cinema screen, it would be unrecognisable. I don't remember the shots you are talking about, but I'd say it is almost definite they were taken with a much better camera.

this is more of a critisism of the last answer, more than an answer to the original question. photos taken by and traditional 35mm camera will face the exact same distorsion since the photo-negative is the same. better cameras allow the photographer to take better original pictures due to the fact that they can control and manipulate the light that contacts the negative.

True except that a 35mm negative is about 4 times the size of a negative from an instamatic camera so while the film is the same the magnification required would be much less from 35mm and even less from a 2-1/4, 4x5 or 8x10 camera. I also can't remember the photos you speak of but it would be possible to use the instamatic photos if they were computer enhanced.