Motography (Apr-Dec 1911)

42 MOTOGRAPHY Vol. V, No. 4. Any questions relating to lenses will be fully answered in these pages. HERBST BRIGHT LIGHT PICTURES. A query comes from Nevada regarding the Herbst Bright Light System. The inquirer is running a dance hall and shows two reels of film nightly. Of course when the lights are out for the projection of the pictures the dancing has to stop. It is desired to run the pictures and have the lights burning so. that the dancing will not have to stop. The Herbst system is a new idea whereby pictures may be shown with the house lights burning. The writer attended an exhibition of these pictures recently, and although all of the house lights were not burning there was enough light in the theater so that a newspaper could be readwithout difficulty. The picture was not so brilliant as in the ordinary darkroom exhibition. It would be sufficiently bright for the dance hall ; if most of the people are dancing they \ \ 1 RT7-TRT7T T / \ / \ 3 4 Fig. 9. will not be as particular about the quality of projection as the regular theater audience. ■• The picture is produced by the aid of some mechanism attached to the regular projection outfit. I have not seen the machine but from descriptions I understand it to be as follows : An extra lamphouse is placed beside the regular lamphouse. In the slide carrier of this lamphouse is placed a slide with a black or opaque center such as shown in Fig. 8. This slide is projected upon the curtain and shows a large black center with a band of white light around it. The motion picture is now projected on the black center. The white band of light appears to absorb the rays of the house lights so that they do not interfere with the picture. This is merely the principle of operation of the system. The Herbst people are about to establish a representative with an outfit in Denver, so that if you are further interested you could see the machine at work, or you can write to me and I can send you the address of their representative privately. MERCURY ARC RECTIFIERS. An inquiry from Conneaut, Ohio, asks about the mercury arc rectifier. The inquirer is using alternating current, but he complains about the noise of the arc and wants to know if the rectifier will stop it. Mercury arc rectifiers have been in use for a number of years and have lately been put into use for projection work. They change alternating current into, direct current. The theory of the rectifier is as follows : Suppose the air is practically exhausted from a glass bulb or tube which has several electrodes of mercury, and containing mercury vapor. This vapor will offer a very high resistance to the passage of any current — so much so, tjiat it may be considered a nonconductor. If the tube is shaken the mercury will bridge the space between the electrodes and form a circuit. If voltage is applied at the electrodes curlent will flow, and when the mercury runs back and breaks the metallic circuit, an arc is formed and ionizes the mercury vapor, which will now allow current to flow one way, but remains practically a non-conductor to the passage of current in the opposite direction. The substance of the above is that mercury will allow current to pass through it in only one direction. In Fig. 9 the dotted line represents the zero point and the curve at X represents the wave form of the primary current. By looking at this curve we can see how the current pulsates. At 2 we have the wave of the current in the left hand anode. At 3 is the wave of the current in the right hand anode. By combining these we have the rectified current wave at 4. These waves would touch the zero mark, but by means oi reactance in the circuit the arc is maintained and carried over. It tends to keep the current at the same value, and if it starts to die away the reactance will tend to sustain or keep it flowing. The result is the wave at 4 always above the zero line. The absence of the pulsations quiets the arc." While not as quiet and steady as with direct current, the greater part of the noise is eliminated. ^/ants Picture Snows Lighted That the darkness of the moving picture theater covers many crimes which have a part in creating the social evil, was the argument of the Rev. M. H. Lichliter, at the Maple Avenue Methodist Episcopal Church, St. Louis. "I am not an enemy of the moving picture show," said Mr. Lichliter, "but I recently made a tour of the shows with good reputations, and I saw sights which would have led me to arrest eight men if I had been invested with police authority." The minister went on to say he believed the invention making it possible to show the picture in a lightened room would do away with much wrong-doing. Texas ^^Vorkers to be Entertained Moving pictures for the employes of the Elephant Butte dam is one of the amusement enterprises the reclamation service officers are planning. A club room will be established for the men and the •canned drama attachment will be operated for the mutual benefit of all the employes.