The aspect ratio of a standard 35 millimeter frame is around 1.37:1, although cameramen may use only the part of the frame which will be visible on a television screen (which is 1.33:1 for standard television). Viewfinders are typically inscribed with a number of frame guides, for various ratios.

Note that aspect ratio refers here to the projected image. There are various ways of producing a widescreen image of any given proportion.

• Anamorphic: used by Cinemascope, Panavision and others. Anamorphic camera lenses compress the image horizontally so that it fits a standard frame, and anamorphic projection lenses restore the image and spread it over the wide screen. The picture quality is reduced because the image is stretched to twice the original area, but improvements in film and lenses have made this less noticeable.

• Masked: the film is shot in standard ratio, but the top and bottom of the picture are masked off by mattes in the projector. Alternatively, a hard matte in the camera may be used to mask off those areas while filming. Once again the picture quality is reduced because only part of the image is being expanded to full height. Sometimes films are designed to be shown in cinemas in masked widescreen format but the full unmasked frame is used for television. A low-budget movie called Secret File: Hollywood, often ridiculed as a collection of bloopers, is actually an example of a film that is always projected wrong. All the lights and microphone booms visible above the actors should be concealed by a projection matte, creating an image that would fill a wide screen for little money.

• Multiple camera/projector: the Cinerama system originally involved shooting with three synchronized cameras locked together side by side, and projecting the three resulting films on a curved screen with three synchronized projectors. Later Cinerama movies were shot in super anamorphic (see below), and the resultant widescreen image was divided into three by optical printer lenses to produce the final threefold prints. The technical drawbacks of Cinerama are discussed in its own article.

• Big film format: a 70mm film frame is not only twice as wide as a standard frame but also has greater height. Shooting and projecting a film in 70mm therefore gives more than twice the image area of non-anamorphic 35mm film with no loss of quality.

• Super anamorphic: 70mm with anamorphic lenses creates an even wider high-quality picture.

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