35 mm anamorphic – This type of widescreen is used for CinemaScope, Panavision, and several other equivalent processes. The film is essentially shot "squeezed", so that the actors appear vertically elongated on the actual film. A special lens inside the projector unsqueezes the image so that it will appear normal. Films shot in CinemaScope or Panavision are usually projected at a aspect ratio, though the historical aspect ratio can be 2.55:1 (original 4-track magnetic sound aspect ratio) or 2.35:1 (original mono optical sound aspect ratio). The negative is usually 2.66:1 or, in rare cases, 2.55:1 or 2.35:1. The sole purpose of the change to 2.39:1 and, later, to 2.40:1, was to better hide so-called "negative assembly" splices (splices employed in the composited camera negative. This was not a production change, rather it was a recommended projection change.)