Stereoscopic Motion-Picture Camera

a motion-picture camera with two lenses, designed for stereoscopic motion-picture filming; it is usually a modified version of a professional motion-picture camera with specific design changes and added attachments.

Figure 1 shows the optical system of a stereoscopic motion-picture camera that uses 35-mm film; the system includes two lenses with prism attachments. During filming, the film receives the right and left images of a stereopair, registered one above the other. The film is advanced in steps equal to twice the frame height. The stereoscopic base length can be altered by means of various prism attachments, and interchangeable lenses are used to change the scale of the image. Each pair of lenses is equipped with devices that simultaneously change the relative apertures of the lenses and adjust the focus. The design includes provisions for changing the optical axes of the lenses in order to achieve convergence of the sighting axes.

Figure 1. Optical diagram of a stereoscopic motion-picture camera. Light rays emanating from the object being filmed pass through a prism (1), are successively reflected by the two reflecting surfaces a and £>, and then pass through a lens (2), which projects an image of the object onto film (3). The second image of the stereopair is projected onto the film by a second lens, which has an identical prism system.

Stereoscopic motion-picture cameras are equipped with stereoscopic viewfinders, through which the camera operator sees a three-dimensional image of the objects being filmed. In stereoscopic filming with 70-mm film, the right and left images of a stereopair are registered side by side across the width of the film.