International projectionist (Oct 1931-Sept 1933)

May 1933 INTERNATIONAL PROJECTIONIST 13 per cent? In tihe same way he goes on to say that in the case of singlephase the motor generator efficiency is not so high — yet as an example he cites a figure of 75 per cent. — that is, equal to the upper limit he has just stated for a three-phase set. It should also be known that the standard efficiency of a mercury arc at half load lies between 77 and 80 per cent, which is considerably higher than the average motor generator performance figure. The losses of a rectifier installation can be decreased by a further 20 per cent if stabilizing choke coils are employed to reduce the resistance losses, thus giving still a very much increased overall efficiency (about 15 per cent) over that possible with the most efficient motor generator set. My impression is that to find which converter gives better light results for projection, the best method is to measure it. I have witnessed such tests and they showed the rectifier to advantage. To talk of the smoothing chokes being a possible source of trouble is just silly. One might as well say that the connecting leads from the equipment to the load are also another possible source of trouble (undoubtedly true but silly). Again, one of the many advantages of the Mercury Arc isthe negligible voltage drop experienced under working conditions, and if your contributor took the trouble to read the announcements which he sets out to criticize, he would know that a rectifier can be equipped with any range of voltage control desired. Operating Noise Levels With regard to noise, most manufacturers of motor generator sets may give certain guarantees regarding noise on their machines and it may be possible, by suitable mounting, to eliminate objectionable noise entering the building from the motor genera tor set. And what may be offered in all good faith as a noiseless machine may not prove sufficiently silent when installed. After all, motor generators are rotating machines and there must always be a certain amount of noise associated with such an equipment. A rectifier might prove noisy due to magnetic hum; but then there is something wrong and can be corrected and altered, therefore, it is easiest to solve this problem of noise by employing a static rectifier. The question of space is, of course, a point for the rectifier, as where there is very limited space the rectifier is probably the only solution. I agree with your contributor that to put a rectifier or motor generator in some out of the way corner, where nobody can get at it easily, is bad engineering practice — if there be plenty of room available. But after all, we live in an imperfect world where we can't have had all the room we want and it is certainly to the advantage PRODUCTION PROCESS FOR ANIMATED CARTOONS William Garity WALT DISNEY STUDIOS, HOLLYWOOD, CALIFORNIA Always important to the well-balanced motion picture program, the animated cartoon benefited tremendously through a clever utilization of sound accompaniments and, lately, through color. Probably -the outstanding motion picture cartoons are the Mickey Mo2ise and Silly Symphony subjects produced by Walt Disney Studios, and the accompanying paper by Mr. Garity, originally presented to the Pacific Coast Section of the S. M. P. E., expl^ns in detail the production process at these studios. — Editor. II WHEN the animator has completed his particular scene, the drawings are turned over to the Inking snd Painting Department, the function of which is to transfer or trace each drawing on celluloid sheets. These celluloid sheets are the approximate size of the paper, and about 5/lOOOths of an inch in thickness. They are perforated with registering holes, identical to those in the drawing paper. The paper drawings are placed on the registering pins, the celluloid sheet is superimposed on the drawing, and a veiy careful tracing of the drawing is made with black India ink. After the tracing of the outline has dried, the celluloid is reversed, and the entire area occupied by the figures on the drawing is made opaque with paint. The primary reason for using celluloids is an economic one. If the transparency were not used, it would be necessary to draw a complete background for each frame of the picture, which, of course, would be an economic impossibility. To avoid doing this, a single background is drawn, the characters working against this background being traced on the cellu loid sheets. As the entire area occupied by the character is rendered opaque, the background is completely matted out by the character when the celluloid sheets, inked and painted, are superimposed on the background. It is possible to have a large number of characters, each doing something different, by tracing each character on a separate sheet of celluloid, and simultaneously superimposing these celluloid sheets upon the background. The use of many such celluloid sheets aggravates the photographic problems, due to the light losses and color changes introduced by the celluloid. Four sheets seem to be the greatest number that may be used without seriously affecting the photography. For rendering the celluloid sheets opaque, white, black, and five shades of gray paint are used. When a number of characters are superimposed simultaneously on the background, 1, 2, 3, or 4 sheets of celluloid are used. In order to produce the same color value in the negative, five different shades of gray paint must be employed. The darkest shade is used on the top sheet and the lightest on the background. This is necessary because of transmission losses inherent to the celluloid. The thickness of the sheet is also a factor to be considered: and for that reason all sheets are carefully graded as to thickness and color, in order to minimize the painting problems and reduce density changes in the half-tones of the film. After the picture is photographed, all traces of the ink lines and of the paint are removed by washing, thus reclaiming the sheets for later use. In practice, the celluloid sheets are never (Continued on page 29) of the rectifier that it can be placed anywhere and give no trouble. The extra cost involved in the upkeep of a motor generator such as replacing brushes, oil on the bearings, grinding of commutators, etc., is certainly another point in favor of the rectifier, even if the motor generator results are so good as those obtained in the theatre in which your contributor is interested. In conclusion, let jme say that I am not at all averse to motor generators and am not unmindful of the very good work they have done and are do ing; but if people want to be helpful in contributing to a discussion on their merits, let us have at least consistency, and if possible, accuracy. The motor generator for all larger work v/as long ago superseded by the rotary converter and motor converter, which in turn have been superseded by the rectifier for the most strenuous and important public supply duties — on light and power distribution networks, on tramways and railway systems. To say, therefore, that the rectifier still is on trial is, to say the least, absurd.