Motography (Jan-Jun 1918)

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Makch 2, 1918. MOTOGRAPHY 433 Solution of Projection Problems HOW TO OBTAIN THE BEST RESULTS DESCRIBED IN DETAIL How to Determine the Right Size Lens Good Rule to Remember Is Given by Motography Expert, Clearing Up Difficulty That May Be Experienced by Many BY J. WESLEY SMITH LYKES MANSELL of Trinity, Tex., asks a question this week, the answer •of which may solve difficulties for many ■others as well. Below will be found Mr. Mansell's question, the answer, and questions and answers of others : Q — I have been running one Powers 6A machine for about three years and have had to throw a picture on the screen which was about SO feet from the machine. Now my boss has moved into a new building and I have to throw the picture about 65 feet. He wants to get a picture about 9x12. Now what size lens will I have to get? I am using a 4j4-inch size now, but it makes the picture too large for the screen. And what size condensors would be best? I am installing another machine now and I would like very much for you to tell me if it is possible to hook two machines up with one compensarc? We are using 110 volts A. C. current on a compensarc. A — A good rule to remember regarding the size lens to be used for a given throw i --jjjPjCiB p8§ rM \^Mf^TmS *# /Jm flPWtll « ./4B£$Sftk /£M H 111 / nS \ /fl 1 III // ^ tli III 1 pp 1.1 Wt'b "" \y^jj^yi^^p^ Sv ^ I V MJr and specified size picture is this : Divide the length of throw by the width of picture desired and the quotient or answer will be the size lens required. Thus in your Case the throw is 65 feet and the width of the picture wanted is 12 feet. Sixty-five feet divided by 12 feet is 5 5/12. You will need either a 5j4-inch or 5j^-inch lens. For a picture slightly smaller than 12 feet use the 5^-inch lens and for a slightly larger picture use a 5j4-inch lens. The angle of divergence in different makes of lenses varies slightly, but in your case any standard make will be all right. I feel positive that any reputable house will send you both of the above lenses to try out. Return to them the lens not suited for your picture. The question regarding the proper size condensor is mostly a matter of experiment, but would advise you to purchase a pair of 6^2-inch and a pair of 7^-inch condensors. You will have to try different combinations of the above condensors until your field is uniformly illuminated, but remember, always place the smallest size lens nearest the arc. Yes, you can hook up both machines to the same compensarc, but do not burn both machines at once for more than a few seconds at a time, as you will overload the compensarc and will probably burn it out. Not only that, but the illumination of the picture on the screen will drop while the other machine is burning. Q — For the last few days the pictures I have been showing are not as clear as formerly. They do not seem to be out of Latest model of the Motiograph. focus, yet at the same time are not clear. This is especially noticeable in the titles, as the bottom of the letters seem to run. Kindly let me know where my trouble lies. A — Your last description of the trouble makes this a very easy matter to fix and can be told in very few words. The whole trouble is that your shutter is out of time with your intermittent and the film is starting to move at the aperature before the shutter is entirely closed. Benjamin Chapin Turns Inventor Works Out Novel Combination of Lights Whereby Lack of Contrast in Costume Is Largely Overcome ■Gear case of the latest model of the Motiograph open and showing pulley gearing and motor drive. BENJAMIN CHAPIN, the star, was dissatisfied with any lights that he could purchase for getting certain effects "close up," so he evolved a combination himself. Conferring with his technical director and chief electrician, he outlined his invention and instructed them to make the new bank out of parts of Cooper Hewitt banks. "As you doubtless know," explained Mr. Chapin later, "the character of Abraham Lincoln, which I portray in "The Son of Democracy," is a very difficult subject to photograph for various reasons. "In numerous tests I noticed that the black beard was hard to be distinguished from the black coat. I figured that if I could get sufficient light from underneath it would act as a back light and throw the dark outlines into relief. When the combination bank was made and tested it proved to be just as I anticipated and gave wonderful results, which can be especially noticed in our recent 'close-ups.' The effect is a soft natural tone which we could not get in the glare of carbon lamps generally used in these close-up scenes."