The Moving Picture World (1907)

Record Details:

Something wrong or inaccurate about this page? Let us Know!

Thanks for helping us continually improve the quality of the Lantern search engine for all of our users! We have millions of scanned pages, so user reports are incredibly helpful for us to identify places where we can improve and update the metadata.

Please describe the issue below, and click "Submit" to send your comments to our team! If you'd prefer, you can also send us an email to mhdl@commarts.wisc.edu with your comments.




We use Optical Character Recognition (OCR) during our scanning and processing workflow to make the content of each page searchable. You can view the automatically generated text below as well as copy and paste individual pieces of text to quote in your own work.

Text recognition is never 100% accurate. Many parts of the scanned page may not be reflected in the OCR text output, including: images, page layout, certain fonts or handwriting.

tlte MOVING PiCfUfcfc WOfcUB. 55 the aid of two lights through the two lenses, which were adjusted so as to superimpose them correctly. Shutters were arranged to alternately expose and obscure the pictures, so that when the "even" picture of one series was fully exposed, the "odd" picture of the other series was fully obscured, and when only a portion of one pic- ture was exposed, the corresponding portion of the other was obscured and the remainder exposed, so that at all times there was a full picture on the screen, that is to say, that the screen was always occupied, either by the pro- jection of a whole picture from one of the films, or the fractional parts of two pictures that composed a whole picture from the two films. In other words, the sum of the portions of the pictures simultaneously exposed amounted to but never exceeded a full picture, and throughout the whole operation there was a continuity of evenly illuminated picture projected, without any break, interval, or obscuration whatever. All these experiments were very interesting and in- structive, and led to discoveries and the' disclosure of difficulties which were never contemplated. I found that when the two lights of low intensity were used, slight differences between them were very noticeable, but when lights of high intensity were employed a much greater difference was not nearly so appreciable. I found also that lenses which, for ordinary purposes, were adjudged to be a pair, would not stand the severe test to which they were subjected in the act of superim- posing the pictures correctly. Objects in the center and at the sides coincided exactly, while those between these ositions were a considerable distance apart. This dis- placement, I concluded, was due to diffraction arising [from the slightly varying curvature of the two lenses. Besides this irregularity the discs of light projected by pie two lenses slightly varied in tint, owing to refractive differences in the quality of glass of which the two lenses were composed. These matters, though apparently pimple, continued to be a great sourpe of trouble until ftheir causes were discovered and ultimately removed. A ppecial pair of lenses subsequently obtained stood the test o well, that two single positive pictures, printed from tie negative, correctly superimposed, and shown alter- nately, exhibited one single picture on the screen so per- fectly that it was impossible to detect that there were alternate projections of two pictures, and that one )icture only was not being shown continuously by a single ens. I at first experienced very great difficulty in per- manently adjusting the projector so as to correctly super- impose the pictures, for however carefully they were fdjusted and appeared to superimpose when the machine ras still, a considerable displacement was shown to exist vhen the machine was operated. I at last discovered pat the only way was to regulate the adjustment screws hile the machine was operating, and in that way I suc- eeded in correctly superimposing them. The expert nents with these machines clearly proved e undoubted advantages of the Duplex system, and owed that there was an entire absence of flickering; C but the apparatus failed to satisfy the strict demands of precision so essential to good results, and for that reason I discarded it. I found:— i. That the two lights were liable to vary in intensity. 2. That the two films, printed separately, were liable to vary with each other in degree of transparency, and 3. That the mechanism employed was too uncertain in its action to be relied upon to operate two separate films with a degree of accuracy necessary to give perfect regis- tration. Attention was therefore to be seriously given to these points before a perfect result could hope to be obtained. It was clear that, in order to get as good registration as in the ordinary machines, the projection must not suffer from imperfect registration through separation of the pictures, but that when they are separated they must continue in every respect to maintain their relative posi- tions in succession throughout the series, that is to say, that when two successive "odd" and "even" pictures of the separate series are adjusted to exactly superimpose, the remaining pictures of the two respective series must also coincide. The conditions for success were therefore:— 1. Continuous even illumination. 2. Perfect registration. To ensure these conditions, it was decided to construct a new set of machines to employ the standard gauge film, corresponding exactly in their mechanical movement and having— 1. One light source to ensure even illumination. 2. One film with two series of pictures to obviate vi- brations in the printing, etc.; and 3. A mechanism with certain mechanical action for correct translation of the film. Since it would never be necessary to use the light in two places at one time, it was apparent that I could divert it to illuminate the two series of pictures alternately with- out any loss or diminution of its intensity. The class of mechanism I elected to employ in these machines, which are now in course of construction, is a modification of that known as "Claw Mechanism." The claws are -operated by cams driven from one driving mechanism, and arranged to be inserted and withdrawn by the opera- tion of the cams on inclined planes, which communicate a rocking motion to the frames carrying the arms and pins. The perforations of the film are at regular mathe- matical distances apart, and when the arms carrying the pins or claws are each placed in the same relative posi- tion to the gates and caused to rise and fall the same mathematical distance, they cannot possibly fail to trans- late the separate parts of the film containing the successive pictures, so as to give perfect registration of the pictures on the screen. There is neither theoretically nor practi- cally any difference in effect between translating two pictures on one film by two successive operations of one claw, and drawing two pictures separately by one opera- tion of each of two claws, providing that such claws be operated exactly alike.