Optical device decrypts the color of Jour de Fête

Optique Thevon S. A. (Montreuil, France) has designed a unique optical system to "decipher" the original color version of a well-known French movie entitled Jour de Fête. Filmed in 1947 by Jacques Tati, the movie was recorded in full color using an experimental and complex process; it was shown only in black and white, however, because supplies of the experimental lenticular film needed to make duplicate color copies were unavailable, and because key information required to reconstitute the

Optical device decrypts the color of Jour de Fête

Roland Roux

Optique Thevon S. A. (Montreuil, France) has designed a unique optical system to "decipher" the original color version of a well-known French movie entitled Jour de Fête. Filmed in 1947 by Jacques Tati, the movie was recorded in full color using an experimental and complex process; it was shown only in black and white, however, because supplies of the experimental lenticular film needed to make duplicate color copies were unavailable, and because key information required to reconstitute the color during projection was lost.1

The movie was made using an embossing process that involves crimping multiple cylindrical lenses onto the film emulsion. During recording the film is oriented with the embossed side toward the camera lens, which includes a trichromatic filter to separate the red, green, and blue primary colors. Each of the cylindrical lenses on the film emulsion thus produces a trichromatic image from the exit pupil of the camera lens that is recorded on the emulsion (see figure on p. 34).

In order to view and copy the recorded images in original color, the film had to be illuminated in a manner identical to that used when it was made. A bright beam of light is required, with color composition similar to the one that recorded the images, and the aperture of the camera lens must also be the same. The embossed film is in a 35-mm format providing an image in a 25-27-mm-diameter circle. The embossing is cylindrical with 525 lenses across the width of the film at intervals of 0.04 mm; the focal length of each lens is equal to the film thickness.

Research by director and cameraman François Ede turned u¥a lens similar to the one used originally by Tati. Measurements made on a Thevon optical bench revealed that the lens has a pupil diameter of 12 mm and focal length of 46 mm. Using this information and almost 100 hours of computer design time the company came u¥with the optical system to be incorporated into a camera for reproducing a color version of the movie. The system uses a tricolor lantern--a white-light source and red, green, and blue filters--to restore the original color image.

The tricolor lantern comprises a 4X telescope with a three-element lens, while the lens used for reproduction is a Gaussian type that has eight elements and a resolution better than 50 lines/ mm across the image surface. Two other lenses are placed in contact with the embossed film to concentrate the light rays back toward the copying lens. All the lenses in the system are antireflection coated.

Jour de Fête was shown in full color on French movie screens for the first time on January 11, 1995. Optique Thevon demonstrated the reproduction system during Opto `95 (Palais des Congrès, Porte Maillot, March 28-30, 1995).

REFERENCE

1. François Ede, Jour de Fête, Cahier du Cinema 1995.

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