 One of the shots in the part where Jack is bouncing a ball against a  wall took several days to film. This was because the shot entailed  the ball bouncing from the wall onto the camera lens as it filmed.  As Stanley Kubrick (qv) was so determined to get this precise  shot, the camera kept rolling while the ball was continually hit  against the wall in the hope of it bouncing back and hitting the  lens. It took everyone on the entire unit having a go at it in  between other shots before the shot was finally achieved after  several days.