Quote Originally Posted by newcan1 View Post
Understood. But the phenomenon I was referring to is this: I focus on an object using the split screen, then I move the camera slightly so I can see the same object on the ground glass, and then I find that the sharpest image of the same object on the ground glass is at a slightly different focusing point.
That's probably beacuse by moving the camera you have placed the object a different distance from the filmplane. A few inches will make a differnce if the object is nearby and the lens is wide open.