Projection engineering (Jan-Dec 1931)

JANUARY, 1931 Page 9 with no fringe. The same number of frames as in the ordinary black and white photography, and the same speed of projection are two obvious advantages claimed by the proponents of this method. However, complications present themselves which may or may not be worked out at some time in the future allowing this method to take its place with — or even replace — the commercial processes now in use. These additive processes have been attempted at their best; that is, in using three colors. If only two colors are used nearly all of the two hundred and thirty colors may be recorded, and the complications are fewer. If the spectrum be roughly divided there will be a light and a dark region. The light region begins at the red and ends at the green, while the dark region begins at the green and ends at the violet beyond the blue. In the two color process of the additive method, one color which lies near the beginning of each region is selected. Bright red may be selected to represent the light region, while a green may represent the dark. However, certain natural colors may never be obtained by this method. If red and green be the base colors, yellow, blue or violet will not register as such. If blue be the base color of the dark region, green will not record upon the film as green. If orange be the base color for the light region, bright red will not photograph as red. While less complicated, limitations are imposed when the two color method is used. The speed, both of photography and projection is appreciably reduced by this method. Multicolor and Technicolor The two principal color methods in Hollywood which are operating commercially today, Multicolor and Technicolor, are both subtractive two-color processes. The Multicolor base colors are orange-red and blue. In contrast to the Technicolor method, Multicolor uses the standard motion picture camera without the addition of any filters or prisms. The company furnishes an attachment which is reasonably inexpensive, and a special magazine threaded with two films. These two films are placed emulsion to emulsion, so that the light shining through the lens strikes the celluloid side of the first film. The front film is so treated in the emulsion that it records only the dark end of the spectrum. A blue green picture of the object is impressed upon the first film. The emulsion of the front film is surface dyed red, so that in addition to recording the dark end of the spectrum it also acts as a color filter for the rear film. A red-orange color picture appears upon the back film. The two films are separated, developed, and a print made upon a film coated upon both sides. The record now consists of a film which contains a latent blue-green image upon one side, and a latent orange-red image upon the other. This film then goes through a chemical process in which the pictures upon one side of the film turn red, and those upon the other side turn blue-green. Contrasted with the dye process of Technicolor, this is a chemical conversion process. The actual chemicals which comprise the picture record are converted into other chemicals to make up the desired color photo. Many practical objections arose to this double coated film. It was claimed, and the claims upheld by practice that the film would scratch easily, break and crack, and quickly wear out. The Multicolor Corporation developed a special shellac with which the film was treated and which overcame the objections noted. With the Multicolor process it is impossible to obtain a bright red or yellow, but a very beautiful gold is obtained which closely approaches yellow. It might be noted in passing that if lighting conditions be perfect, it is possible to obtain a yellow, but under ordinary studio conditions, it is not practicable. The same difficulty is present in obtaining violet and purple. The green has a slight bluish tinge. Outdoor scenes when photographed in Multicolor are exceptionally beautiful. The blue of sea or sky seems to impress itself particularly well in this method, which is a distinct advantage and does much to recommend the method for outdoor work. One of the most beautiful motion picture shots which it has been my pleasure ever to witness was a Multicolor shot of a lake over which was thrown a gorgeous streak of golden moonlight. The combination of the dark of the lake and the gold of the moonlight was one which will always remain in memory as a vivid example of what is possible with color photography. The Technicolor method uses a specially built camera, equipped with a special single lens and a set of prisms arranged so that the separate and individual color pictures are thrown upon successive frames of the same film. A revolving color filter is placed so that the one red and one green picture are photographed simultaneously. Thus, when the film is developed, there are two color sequences present upon the same film. Each set of color records is printed upon a separate positive — the red upon one and the green upon another. These prints are developed and fixed in the regular way. Each is then treated so that the silver images are concerted into mordanted images — that is, images which have the property of absorbing certain dyes. The positive having the red record is dyed green, while the print having the green record is dyed red. Then, a fresh film which is coated with a specially pre pared gelatine is pressed successfully against the two prints. This gelatine absorbs the dye from the prints in the same manner that newsprint paper absorbs ink. The process of transfer of the image to the single gelatine coated film is called imbibition — referring to the property of the gelatine to imbibe the dye from the dyed film. Ordinary lithographing embraces the same process. The two color records, having now been transferred to the same side of one film, are ready for projection. A tremendous advantage of the Technicolor process is that no new attachments are necessary for the projection machine. The prints contain their own color and may be projected upon any ordinary machine. There are certain outstanding disadvantages to this process. The dye tends to spread in the imbibition operation, much as ink spreads on the cheaper grades of newsprint paper, tending to make a hazy outline ; each print will vary from another due to a slight difference in time it is allowed to remain in the bath, and there are certain natural colors which may never be obtained with this process. Red and green being the base colors of the Technicolor process, it is impossible to obtain a true blue, yellow or violet. Yellow will appear orange upon the screen. The final print contains the actual color upon the film and the combination of red and green will give a very close approximation to the natural color of the object. However, the two color process can never give as true a representation as the three, and the development of a commercially possible three color process is the aim of those connected with the color companies. Summary In conclusion, a brief comparison of these two methods, Multicolor and Technicolor, may be of interest. A great advantage of the chemical conversion method is that it is a process which goes to completion and stops. The amount of color does not vary from print to print, while in the dye process the amount of dye and the length of time the print remains in the dye bath determine the shadings and the amount of color which will be present in that individual print. Due to lack of imbibition, there is more definition to a chemical conversion print than there is to a dye process print. The dye process, however, has the advantage that it is able to register reds, which contributes much to scenes often encountered in motion picture photography. Many studios, as well as companies formed for the express purpose, are at this time at work upon individual methods of color photography, and the future promises to bring out many interesting developments in this field of the motion picture industry.