The procedure for obtaining the lenticular elements in relief required a series of steps: starting from three black and white positive color separations, obtained with any of the available methods, three matrices were printed, from which the film to be used for the projection was finally obtained. The distinguishing characteristic of the process becomes apparent in the last two phases: the matrices were obtained by optical printing, with a process that lead to the formation of the lenticular elements. Each of the matrices thus obtained had reflecting elements impressed only in the parts of the image that contained the respective color, while the other parts remained transparent. By subsequently printing the three matrices, in perfect overlap, on any transparent plastic material (not only cellulose, but also cellophane or other similar substances), the support to be used for projection was obtained, in which the shape, size and orientation of the lenticules corresponded to the chromatic tonality of each section of the reproduced image. Unlike other lenticular processes in use at the time, characterized by a uniform distribution of the optical elements, in the Bocca-Rudatis process the lenticules were shaped specifically for the image to be reproduced; thanks to this innovation, the intensity, saturation and color of the subject were fixed on the support through the infinite variations of shape, orientation and size of the lenticules. In practice, the lenticular elements corresponded to microscopic pyramids differentiated according to the color to be transmitted: each pyramid consisted of two to six spherical or cylindrical faces, based on the refractions to be made. Obtained by optical and chemical methods, they were completely transparent and only about four microns large, corresponding to over sixty thousand elements per square millimeter.
In passing from the set of negatives produced by the camera to the support used for projection, the photographic image disappeared. The lenticular film was in fact completely transparent. It was not the more or less intense blackening of the image that allowed the additive reconstruction of the colors in projection, but the individual lenticular elements, which refracted the beam of light sent by the projector.
In areas without color, i.e. blacks and shadows, the support had no lenticular elements: the light that passed through them didn’t undergo any refraction and proceeded in a straight line. To prevent it from reaching the screen, radically altering the chiaroscuro values of the image, it was intercepted by an opaque screen. The superimposition of all the selections obtained on the screen, with the exception of the dark areas, reproduced the original colors of the subject, without any chromatic alterations. A method for controlling the chiaroscuro values considered more versatile than the opaque disk consisted in a black and white image printed on the film strip; in this case, the rays corresponding to the dark parts were blocked directly by the blacks and a greater amount of light was allowed to pass, causing, however, a loss of purity and saturation in the projected colors.
Pierotti, Federico (2016): Un’archeologia del colore nel cinema italiano. Dal Technicolor ad Antonioni. Pisa: Edizioni ETS, p. 103-105.
Translated and adapted by Noemi Daugaard, SNSF Film Colors. Technologies, Cultures, Institutions.
Original Technical Papers and Primary Sources
Rudatis, Domenico (1939): Esigenze artistiche e direttive industriali del film a colori. In: Cinema, 63, p. 72.
Cauda, Ernesto (1938): Il cinema a colori. Quaderno mensile. Roma: Bianco e nero, anno II, nr. 11, on pp. 82–89. (in Italian)
Luppi, Livio (1954): Dizionarietto tecnico del colore. In: Giuseppe Sala (ed.): Bianco e Nero. Il colore nel cinema. Rassegna mensile di studi cinematografici, XV,2-4, pp. 177–236, on pp. 185–186. (in Italian)
Pierotti, Federico (2016): Un’archeologia del colore nel cinema italiano. Dal Technicolor ad Antonioni. Pisa: Edizioni ETS, on pp. 79–83and on pp. 103–105. (in Italian)
Arnheim, Rudolf (1938): Il nuovo sistema italiano per la cinematografia a colori naturali. In: Cinema, 47, pp. 370–372. (In Italian)
Cauda, Ernesto (1938): Il cinema a colori. Quaderno mensile. Roma: Bianco e nero, anno II, nr. 11, on p. 104.) (in Italian)
Poggetti, A. (1938): Verso la vittoria del colore. In: Cine Teatro Radio Magazzino, 78, p.2. (In Italian)