Motion Picture News (Jan - Mar 1928)

March 10. I !J ;J S 839 Projection V% Optics, Electricity, Practical Ideas & Advice Inquiries and Comments A Praclical Consideration of Some Cow moil Projection Faults i T the last mcetiiifi: of the Society of Motion Picture Enfjiu^ineers, held at Ijake Phicid, N. Y., dnriiif;: the last week in Septenihei', 1927, a paper of special intei-est to projectionists was presented by Arthur Gray, Supervisor of Pix>jeeti()n at Lancaster Theatre, Boston. Gray's paper, "Practical Needs in Projection"" !)roujjht up a number of points which had to do with the condition of film as received by theatres from the exchanges and described the effects of defective film — if it may be so referred to — ^on projection results. Much of his paper had to do with the ill effects of "buckled" film, it being brought out that such buckling was the direct result of greatly increased heat energy being passed through the film by use of reflector ai'C illuminators. In the extended discussion which followed the reading of the paper, it was generally agreed that the primary reason for film buckling was due to improper drying of the film before it left the exchanges, although one party to the discussion advanced the suggestion that this imperfect condition of the film was likely to result even after shipment from the exchange had been made, since exposui'e to moist atmospheric conditions Avould cause the film to absorb moisture. Gray, in his paper, first took up the subject of splices, going on to say that very few exchange-made splices were properly made and invariably came apart when the film was being projected. We shall quote largely from his paper in order to present his findings to the readers. ExcJiange Inspection Does Not Rem,ove All Poor Splices ' ' Despite the improved methods of inspecting film at the exchanges, and the repairs which are made prior to shipment, it is the general experience of projectionists with whom I have discussed the matter that the print invariably must be re-examined at the theatre before being projected if a reasonable assurance against the film breaking while in the projector is to be had. They have learned that, while most of the loose splices are detected and removed at the exchange, some of them are not, and it requii-es only a single splice separating while in the projector to stop the show. The competent projectionist classifies this kind of accident as just about the worst |K)ssil)h' lliiiig whicii can lia|)pen in his work, and yet despite all the routine precautions whicli are taken to prevent it, mishaps of this luiture continue to occur. There are so many splices in sonu prints, especially those with numerous color inserts, that not all of tlieiu receive thi! frequent attention which is necessary to detect the first signs of them loosening up, and when once a splice has started to loosen, it is a menace until re-made. The fewer splices there are in a jirint, the less probable cause for trouble there will be; and, in making up prints, any planning which will keep the necessary number of splices at the minimum is desirable. Many Laboratory Splices Are Improperly Made It is my exi>erience and, I think, the general one among j)rojectionists, that the kind of loose splice which gives the nu)st trouble is the machine-made laboratory splice. In our projection room at the Lancaster Theatre, a record is kept of the amount and kind of repair work necessary to the film which we project, and some of the data may be of interest. Table I Lancii^ter Theatre Film Inspection Record for Three jMonths' Period Feet Footage of film used 411,653 Total of number of splices 6,892 Total number of splices re-made.. 211 Nature of Defects in Splices Number Loosened 133 Unmatched Perforations 10 Damaged Perforations 5 Wide or Cui'led 51 Cracked along splice 12 Of the total number of splices' that were re-made, 133, or 63 per cent of them, were re-made because they were either in a loosened condition when received from the exchange or else began to open up during the three-days' run of the print. Intermittent Movement of Film Must Be Accurate Trouble of a more technical nature, which are of recent development, and which concern the position in which the film frames seat at the film aperture, are giving many projectionists, and probably some who are not projectionists, considerable food for thought. The placing in rapid succession of many thousands of film images at the aperture during the projection of a picture is a precise job. The mechanical process of doing this must be pretty nearly right and so. likewise, must be I he film. Kach -ucccs.sivc frame of film must be brought 1o an abrupt stop at the afjerture in virtually the same f)osition occui)ied by all the preceding frames. The permissible toleratice for displacement of any frame or series of frames from this common position is very slig'lit if [>rojection I'aults of a certain nature are to be avoided. Tension applied along the film trjicks on the projector oi)erates to rmiintain thft frame of film in a flat plane at the aperture. Opposed to this tension is a tendency f(jr the film to flex in the direction of the light source and assume a sort of "cupped" position while motionless in thf 'ight ray. The amount of bulge that will ( ur will depend upon certain characteris js of the (ihu stock, the amount of hes incident on the film, and the i>liotograp! .c density of the film image. Large Aperture Lens Requires ReFocusing So long as the film is in normal condition and continues to seat in a normal manner at the film aperture, the projection lens will focas all of the frame images equally, and the picture ^vill appear shai-p and well defined. Under conditions where the projection lens is working at a large relative aperture and consequently with a depth of focus that is slight, it may be necessary occasionally to re-focus the lens when pronounced changes in film density occur. This may re(|uire considerable attention, while the act of doing this will be noticeable on the screen unless carefully performed. However, the point I want to make is that when the film, which is in a normal condition, is being projected, the control of the focus of the picture is in the hands of the pi-ojectionist, and it is his own error if the lens is not re-adjusted when it should be. Buckled Film Causes In-And-OutOf-Focus Effect on Screen With film which is in a buckled condition, a very different and difficult situation is encountered. The term, "buckled film," is here used to designate film which has a decided tendency to flex just in one direction and then the other in a rapid and irregular manner while passing the film gate of the projector — this, regardless of the tension which is applied to it in the projection mechanism. One sequence of frames will seat at the aperture as they should, another series may folloM which will not, projection being accompanied by a distinctive rattling sound that is characteristic of film in this condition. The maximimi difference in displacement between these frames, which head in altei-nate directions, is too great for the lens to accommodate, and a pi*onounced inand-out-of-focus effect is experienced on the (Continued on follozuing page) M S t M 11 M 4 4 S fl 14 n 14 If 11 >i ss 11 M s u . 11 4 11 11 "l U 1 . 18 .e 10 :. s* . ts {.19 pt. 9 y • c 16 :t. 14 >T. II icwed [ar. 3 OT. U OT. i