Negative pulldown is the manner in which an image is exposed on a film stock, described in the number of film perforations spanned by an individual frame. It can also describe the orientation of the image on the negative, whether it is captured horizontally or vertically. Changing the number of exposed perforations allows a cinematographer to change both the aspect ratio of the image and the size of the area on the film stock that the image occupies (which affects image clarity).