Motography (Jan-Jun 1918)

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380 MOTOGRAPHY Vol. XIX, No. 8 erate Mazda projector lamps without properly designed regulators. For alternating current service the Argus alternating current regulator is most efficient, transforming alternating current line voltage to the voltage and operating current of Mazda projector lamps at an efficiency of approximately 88 per cent. For direct current service the Argus direct current regulator is designed for reducing the line voltage of direct current circuits to the voltage and operating current of Mazda projector lamps. These are not as efficient as Argus alternating current regulators, on account of the resistance dissipating considerable wattage. i General conditions under which carbon-arc motion picture propection machine arc lamps can be displaced by the present types of Mazda projector lamps as recommended by the Mazda lamp engineers after two years' successful experience, are as follows: When alternating current is used: If a compensarc, transformer, economizer or rheostat is being used with the carbonarc equipment the resulting screen intensity will be such that usually the Sheck universal adapter, with the present types of Mazda projector lamps, can be installed with very satisfactory and comparable screen illumination where the length of throw is less than 100 feet from the projection lens to the screen, if the size of the picture is no wider than 14 feet. If alternating current service is used with a mercury-arc rectifier and less than 40 amperes of current is used at the arc, the same recommendation applies. On direct current service: This means either direct current service secured from the line and at present controlled through a rheostat for the operation of the present carbon-arc equipment or where the line voltage is alternating current and direct current service is secured by the use of a motor generator set. If exhibitors are now using 35 amperes of current or less at the arc, present types of Mazda projector lamps will produce satisfactory screen results where the length of throw does not exceed 90 feet and the width of the picture 14 feet, but not over 35 amperes. It is important to secure information relating to present carbon-arc equipment and projection conditions before making definite statements or recommendations regarding the performance of present types of Mazda projector lamps. The recommendations given are entirely general and it is advisable to get complete information before making definite recommendations. The essential information to obtain is: (1) The line voltage. (2) Whether direct current or alternating current. (3) If alternating current, find out if it is 60-cycle or 25-cycle service. Different types of Argus alternating current regulators are necessary for 60 and 25cycle alternating current circuits. (4) Secure information in reference to the kind of compensarc, transformer, economizer, rheostat or motor generator set in service at present. (5) Length of throw from screen to projection lens. (6) Size of the picture thrown on the screen (not the size of screen). (7) Kind and description of screen. (8) Size of projection lens used: No. 1, Y\ size, or No. 2, y2 size. Oftentimes wider aperture lenses with Mazda projector lamps will secure increased screen illumination. Information blanks are furnished by the manufacturer for this purpose. The cost of Mazda lamp renewals compares favorably with the cost of arc lamp carbons per 100 hours burning, as with Mazda lamps there is no extra expense for arc lamp parts, carbon jaws, etc. As the special prismatic lens used with Mazda lamps is made of high heat resisting glass there is practically no lens expense. The saving in cost of current will average 75 per cent on alternating current service and the saving in current cost will soon pay for the Argus units and any increased cost for Mazda lamp renewals. You Can Do Almost Anything with Em Will a Ford Car Run a Picture Machine? Asks Reader — It Certainly Will, Motography's Expert Replies By J. WESLEY SMITH I AM ASKED this week, among other things, to tell whether an outfit consisting of a Ford automobile and a dynamo could be used to operate a projection machine. After writing an answer in the affirmative I learned that such a combination already has been used, but I am unable to supply the name of the exhibitor. I am informed that my opinions, which were published in Motography for the first time last week, have brought very favorable comment from prominent theater owners. I am glad to know they like the department. I hope they avail themselves of the opportunity and ask all the questions that are puzzling them. I will be only too glad to give my answers. Peggy Hyland as she appears in "The Debt of Honor," her first picture for William Fox. Q. — Do you think an outfit consisting of a Ford car and a dynamo would make a satisfactory electric lighting outfit for a motion picture machine? If the Ford engine were used to run the dynamo, would it be necessary to buy very much in addition to make the outfit complete? What size dynamo would you recommend? A. — You will be able to make quite a satisfactory lighting equipment with the Ford motor and generator. However, there are many things to be taken into consideration in order to get a steady light, and perhaps the most important one of all is the constant speed of the engine. This is absolutely necessary and there are many things which will slow the speed, as the speed of the engine is in direct proportion to the load, and the voltage will drop or rise as the speed of the motor drops or rises. You will have to purchase at least two pulleys and belt. You do not state what size picture you intend to show or how far the throw will be, but a 60 volt 35 amp. D. C. generator will probably be all that you will require, as this size of generator will give a good 12-foot picture up to 75 feet. Q. — If possible, will you tell me what percentage of light is absorbed by different colored films? A. — Taking the screen illumination as 100 per cent, the percentage of light absorption is approximately as follows: Black and white 8 to 10 per cent. Yellow 20 per cent. Amber, light and dark. 20 to 35 per cent. Blue, light and dark.. 30 to 40 per cent. Green 50 per cent. Purple 60 to 65 per cent. Orange 65 per cent. Red 75 to 80 per cent.