A.Gillett, Henri Chrétien, Jean Tedesco

From the very time of its inception the cinema art seems to have been beset by the rigid limitations implied by the use of an almost square frame, and the sound-track has only accentuated the inharmonious proportions of the screen projection. Hollywood technicians have been fully aware of the aesthetic short-comings of the system. They sought to lessen the height of the picture by developing the "American" frame, bringing the sound screen to about the same size as the silent screen. How is one to overcome the insurmountable limits imposed by the standard size of the film? Instead of a screen five to six meters wide, it is possible to use, for example, a screen ten to twelve meters wide, but the height of the picture will increase accordingly, and what we shall see will be a more or less monstrous enlargement wherein the defects of the film, particularly the graininess, will appear grossly exaggerated.

Such attempts to get away from the conventional system are prompted by a desire to be liberated from the limitations of the exceedingly narrow frame, to suit the diverse needs of an art the very essence of which is motion and space. The technical solution to the problem was not actually attained until the appearance of the French invention of Professor Chrétien.

In discussing this subject, it must be pointed out that it is believed that projection of such dimensions has never before been realized, either in a theatre or outdoors. One of the largest projection screens was built and used by Lumière in 1900 in the Galerie des Machines of the Paris Exposition. It measured 30 meters wide by 24 meters high and required a projection distance of 200 meters (NO1). This panoramic screen had an area of 600 square meters, 60 meters long by 10 meters high. The largest screen constructed for a theatre is that of the Gaumont Palace, which has a normal area of 100 square meters and may be enlarged to 200 square meters when certain scenes of the film being projected permit a panoramic effect.

To obtain sufficient brightness of the projected images, it is necessary, on the one hand, to use extremely powerful arcs and, above all, to consider the problem of the reflective power of the screen. After repeated trials the best results were obtained with a screen consisting of a cloth to which were attached small and perfectly spherical glass beads. However, a beaded cloth of such dimensions could not be practicable for outdoor use. It was therefore necessary to develop a screen capable of withstanding the weather, and it was decided to study the possibility of placing the beads on a wall instead of on a screen.

This particular screen consists, first, of a support of few centimetres thick, consisting of a mixture of lime and sand support upon the screen proper. This coating of varnish was, in turn, covered with six successive layers of zinc white; and, finally, these layers were coated with an adhesive varnish onto which the beads were thrown by means of a special compressed air gun.

The resulting screen is, of course, directional, having its maximum reflectivity within an angle of approximately 43 degrees. Outside the 43-degree angle the reflective power is reduced about one-half. Nevertheless, the screen at the Palace of Light, in its present position, permits an audience of 4000 persons, as a minimum, to enjoy the projection under excellent conditions of visibility and brightness.

One of the greatest difficulties was the problem of image brightness, and it was necessary to take into consideration the surrounding light, as adequate darkness within a radius of 200 or 300 meters around the Palace was entirely out of the question. However, the brightness of this gigantic image is even better than that obtained in many motion picture theatres using projection screens of average dimensions.

The screen was installed on the façade of the Palace of Light, and was exposed to the weather during the period of the Exposition. The facade of the Palace, and the screen itself, were slightly concave, which helped to avoid the marginal distortion that would have occurred had the facade been flat, since the apparatus at the right projected the images on the left of the screen and vice versa.

In order to project films of standard size (18 by 24 mm) upon this large screen, standard, the surface of which measures approximately 600 square meters, new methods, in addition to the use of a screen of great reflective ability, projectors of tremendous power, highly luminous optics, and so forth, had to be adopted. A special difficulty was encountered with respect to the shape of the screen, the width of which was six times the height, whereas the width of the film images barely exceeds the height. This difficulty was overcome by the use of two connecting projectors, each equipped with a special optical device known as the "Hypergonar".

The Hypergonar lens was invented in 1927 by Professor Henri Chrétien, of the University and Optical Institute of Paris. Mr Chrétien submitted it to the Optical Society of America some years ago. A description of the apparatus and its new possibilities with regard to motion pictures has been described by H. Dain in the Journal (NO2).

It is a sort of optical transformer. It does not produce real pictures by itself, but if set before an ordinary photographic objective doubles the field of the objective in one direction only, which in this instance is horizontal.

A picture 24 mm. wide may thus be registered on a film that would normally require a 48 mm. picture. When the picture is projected, a similar optical device, placed before the projector, spreads out the luminous beams horizontally, thus restoring the objects to their proper shape. The lenses used are not of the ordinary spherical variety, but are cylindrical, and are more difficult to grind to the required degree of perfection than ordinary lenses.

The total field required to cover the huge screen was obtained by juxtaposing two partial fields, each having been previously doubled by means of the Hypergonar. A special camera-type base permitted the automatic connection of the two equipments in accordance with the focal length of the objectives used and made it possible to drive them synchronously by means of an electric motor.

As a result of the combination of these methods, it was possible to project upon the largest screen in the world, with considerable brightness, pictures that had been magnified six hundred times in height and twelve hundred times in width, or seven million times in area; and this was accomplished in spite of the general illumination prevailing in the surroundings.

Natural vision is thus reconstructed on the screen in a most remarkable manner. Instead of viewing the film through a narrow space - a square loophole - we see it unfolded before us as it would be in nature. No doubt many cinematographic effects are lost through such a panoramic extension, but it is no less true, on the other hand, that with this device many pictures are recreated and endowed with the "aeration" they otherwise lack - the visual extension required to produce this effect, and, in short, the harmony and subtleness of expression of which the cinema had been long deprived - an art which from its very nature and scope was destined to develop freely and at ease after the panorama of nature and life.

The projection proper is provided by two standard Simplex projectors with rear ventilation shutters, which makes it possible to use 250 amperes per arc, without heating the film dangerously. These are driven in synchronism by a third Simplex apparatus, identical to the others, through two universal couplings. The third projector carries also a Thompson sound reproducer. The central projector is driven by a 1 1/2-hp. motor.

As this projection is in a class by itself and requires perfectly homogeneous luminous zones, it was necessary to use extra-luminous Bausch & Lomb condensers to concentrate the light of the arc upon the picture gate. The arcs are fed by a special 800-amp., 110-v. generator, and 16 mm. positive and 11 mm. copper-coated negative carbons are used.

To photograph the scenes two cameras are necessary, each taking simultaneously one-half of the picture. Each camera is equipped with a Hypergonar lens. Each half-image is projected simultaneously by the two outside projectors, the right-hand projector projecting the image on the left-half of the screen, and vice versa. The junction of the two images is smoothed out by special masks consisting of two stationary shutters, the edges of which are cut like the teeth of a saw and set into the light-beams where the latter superimpose. Each of these stationary shutters was set about one meter in front of each projector, on the left and right, outside the beams. The shutters could be adjusted by means of a micrometer screw, thus concealing almost entirely the junction of the two images.

Standard film can be projected by the central projector, the outside projectors merely running idle. The projected image in such case measures 14x10 meters. The distance between the projectors and the screen was approximately 60 meters. Projection occurred daily from 9:30 a.m. to midnight, and the apparatus operated quite satisfactorily.

NO2
Dain, H.: "Memorandum on Widening the Field of Camera Lenses and the Use of Normal Films for the Panoramic Screen," J. Soc. Mot. Pict. Eng., XIX (Dec., 1932), p. 522.

L'écran panoramique et l'équipement utilisés au Palais de Lumière, pendant l'Exposition internationale de 1937

Dès ses débuts, l'esthétique du cinéma a souffert des limitations imposées aux images par le format couramment adopté. Sur la pellicule des films muets, le photogramme était presque carré et, par la suite, l'introduction de la piste sonore n'a fait qu'accentuer les proportions peu harmonieuses de l'image projetée sur l'écran.

Très tôt, les techniciens de l'image, européens et hollywoodiens, ont pris conscience de ce problème. Comment surmonter les limitations imposées par le format standard des films ? Une solution technique fut trouvée par le professeur Henri Chrétien.

A l'Exposition Internationale de Paris de 1937, il s'agissait de projeter sur un écran géant (d'environ 600 m2). Pour cela, il fallait disposer d'un écran aux propriétés particulières (concave, aux qualités de réflexion performantes), de projecteurs de grande puissance et d'optiques très lumineuses (car la distance de projection était de 60 mètres). Les projections devaient avoir lieu chaque jour de 9h 30 à minuit...

Le problème le plus compliqué à résoudre était celui d'élargir le format standard du photogramme (18 par 24mm) en une image projetée aux dimensions panoramiques (proportions de 1 sur 6!). Une solution fut trouvée grâce à l'invention du professeur Henri Chrétien de l'Institut d'Optique de l'Université de Paris: l'Hypergonar.

Il s'agit d'une sorte de "convertisseur" optique qui, placé devant un objectif courant, double le champ dans le sens horizontal. Un système d'optiques cylindriques est utilisé par deux caméras synchronisées lors de la prise de vues. Le même principe est appliqué lors de la projection (deux objectifs cylindriques sont placés devant deux appareils couplés qui projettent de manière synchronisée).

La jonction des deux moitiés d'image est "adoucie" par une fusion obtenue grâce à un cache en forme de scie, placé dans l'axe de la projection.

La pantalla panorámica y el equipamiento utilizados en el Palais de lumière, París, durante la Exposición internacional de 1937

Desde sus comienzos, la estética del cine ha sufrido de los límites impuestos por los formatos habituales de la película a las imágenes proyectadas. Los fotogramas de las películas mudas eran apenas menos que cuadradas. Más tarde, la incorporación de la pista sonora no hizo sino acentuar las proporciones poco armoniosas de la imagen proyectada sobre la pantalla.

Los directores de fotografía, tanto europeos como hollywoodenses, tempranamente tomaron conciencia de estas limitaciones. Cómo sobrellevar los límites impuestos por los formatos estándard de la película? Una solución técnica fué hallada por el profesor Chrétien.

En la exposición internacional de París de 1937, se trataba de proyectar sobre una pantalla gigante (de unos 600 m2).

Para ello, se debía disponer de una pantalla de propiedades particulares (cóncava, con cualidades de reflexión óptimas), de poderosos proyectores así como de objetivos altamente luminosos (ya que la distancia de proyección era de unos 60 metros). Las funciones tenían lugar cada día desde las 9.30 horas hasta medianoche...

El problema más difícil para resolver era el de "ensanchar" el formato estándard de la imagen de la película (18mm por 24mm) hasta lograr una imagen de proyección de dimensión panorámica (en proporción de 1 de alto por 6 de ancho!). La solución fué encontrada gracias al invento del profesor Henri Chrétien del Instituto de óptica de la Universidad de París: el Hypergonar.

Se trata de una especie de "convertidor" óptico que, ubicado delante de un lente corriente, duplica el campo de la imágenen el sentido horizontal. Un sistema de ópticas cilíndricas aplicadas a dos cámaras sincronizadas durante la filmación comprime la imagen en el sentido horizontal. El mismo principio es aplicado durante la proyección (dos objetivos cilíndricos colocados delante de sendos proyectores, sincronizados entre sí, permiten ensanchar la imágen proyectada). La yuxtaposición de las dos semi imágenes es tamizada gracias a un ocultador de borde en forma de sierra colocado delante de los proyectores, del lado donde se encuentran.