Motion-Picture Camera Objective

an optical system for producing a photographic image of an object on motion-picture film. The main criteria for evaluating the quality of the image produced by such an objective are the resolution, the contrast of the image, and the distribution of the intensity of illumination over the field of the frame. The resolution of most such objectives is 45–55 lines per mm in the center of the field and 25–35 lines per mm at the edges. The intensity of illumination at the edges of the field relative to the center of the frame is 40–70 percent.

Most motion-picture camera objectives are anastigmats. They are made in the form of a holder containing a number of lenses (six to seven) and a stop having one principal optical axis. They are characterized by their focal length f’ and aperture ratio 1 n and by the angle of the field of vision 2w.

Depending on the format of the frame and the purpose of the film, a distinction is made among objectives for photographing conventional films (three types: normal, which is a set of objectives with f’ = 28–100 mm, an aperture ratio of 1:2 to 1:2.5, and 2w = 10–22 mm, an aperture ratio of 1:2 to 1:3, and 2w = 107°-63°, for photographing overall views; and long-focus, withf’ = 150–1,000 mm, an aperture ratio of 1:2.8 to 1:6.3, and 2w = 10°-2°, for photographing distant objects); wide-screen objectives (a combination of an objective for photographing conventional films and anamorphic optical systems with cylindrical lenses in the form of filming units and attachments with f’ = 30–500 mm, an aperture ratio of 1:2 to 1:4.5, and 2w = 77°-5°); wide-gauge objectives, with f’ = 28–150 mm, an aperture ratio of 1:2.8 to 1:3.5, and 2w = 91°-22°; narrow-gauge objectives for professional 16-mm filming, with f’ 10–75 mm, an aperture ratio of 1:1.8 to 1:2.8, and 2w = 54°-9°; and amateur 8-mm objectives, with f’ 10–13 mm, an aperture ratio of 1:1.8 to 1:2.8, and 2w = 33°-26°.

There are also special types of objectives for photographing combined frames and stereoscopic panoramas. Objectives having a variable focal length (zoom lenses) are used in each group. They are extensively used in television and motion-picture photography of all kinds, and they are being produced with focal lengths that vary by a factor of 2 to 10 and an aperture ratio of 1:1.8 to 1:3.5.