The American cinematographer (Oct 1933)

240 American Cinematographer • October 1933 CINE ART FILMS ANNOUNCING SIX DRAMAS OF AMERICAN HISTORY Six Reels 16mm Each “With Daniel Boone Thru the Wilderness” “With Ceneral Custer at the Little Big Horn” “With Buffalo Bill on fhe U. P. Trail” “With Davy Crockett at the Fall of the Alamo” “With Sitting Bull at the Spirit Lake Massacre” “With Kit Carson Over the Creat Divide” Also 1 6mm and 8mm MICKEY MOUSE Cartoons Write For Our Catalogue Laboratory Work Complete Laboratory facilities for de- veloping and printing 8mm, 16mm and 35 mm Film. Silent and Sound. HOLLYWOOD FILM ENTERPRISES, INC. 6060 SUNSET BOULEVARD HOLLYWOOD, CALIF. Be sure this trademark is perfo- rated into the main title K I N- O-LUX Users of Kin-O- Lux No. 1 will continue to de- rive satisfactory results with this film during ex- posures.. in bright, sunny weather; however conditions of cloud and haze occasionally found in the fall suggest the use of Kin-O-Lux No. 2—a faster film and only a trifle more expensive. No. 1—100 ft. in green box $3.00 No. 2—100 ft. in red box $3.50 Including Processing, Scratch Proofing and Return Postage KIN-O-LUX, Inc. 105 W. 40 St. New York Mechanical Engineering Applied To Lenses (Continued from Page 21 1 ) lens axis and due to the emerging wave- fronts not being surfaces of revolution). The problems of design are therefore im- mensely more complicated with photo- graphic lenses than they generally are with other optical instruments. The three lens systems shown in Fig. 1 were due to the genius of Mr. Dennis Taylor of Messrs. T. Cooke and Sons of York, under whose name such lenses have always been known, although made at Leicester. His genius produced a form of lens system with aperture f-3.5 com- prising only three glasses but performing in all respects as well as, and in some better than, contemporary lenses of more elaborate construction. Fig. 2 shows a lens system, aperture f-4.5, originally de- vised for photography from aircraft. Figs. 3 and 4 show lens systems both with apertures f-2. Fig. 5 shows a group of finished lenses of various optical designs adapted for dif- ferent special purposes. Fig. 6 shows a large photographic lens used for photo- graphing star fields. It has been usual, for reasons which we shall appreciate later, to employ only spherical surfaces in lens design. Astrono- mical telescope objectives and some others have, however, been “figured” by removing additional material from select- ed zones or areas of the lens, generally by additional polishing, to perfect the per- formance of the lens. But this is very laborious work unsuited to the commer- cial production of photographic lenses generally. Nevertheless it is possible that the next great step in photographic lens design will involve the use of aspher- ical surfaces; but this cannot be effective until the mechanical engineer has pro- vided means for producing such surfaces commercially with an order of accuracy of, say, 0.00001 inch. Optical Class. —The properties which make glass essential for lenses are: its transparency, homogeneity, and perman- ence; the fine polish it will take and re- tain; and the variety of optical properties (refractive and dispersive indices) avail- able according to its composition. Optical glass has been specially made as such since 1 827 by Mantois in France and by Chance Brothers in Birmingham since 1848. About 1881 its manufacture was started in Jena to provide new materials for Professor Abbe’s misroscope objec- tives. During the War a second English factory was established in Derby, and its control was acquired after the War by Sir Charles Parsons (who among other things was an astronomer and son of the celebrated astronomer Lord Rosse), who desired especially to produce large disks for astronomical objectives. Optical glas- ses of the very finest qualities are obtain- able in this country from either Birming- ham or Derby. In producing optical glass, the neces- sary silicate base is fused in a crucible together with the metallic salts which give the glass its special optical properties and the mass is slowly stirred by a mech- anically operated stirring rod. Difficul- ties to be avoided include contamination from pot and rod, segregation of the glass constituents and the inclusion of bubbles and dirt. As it has not been found practicable to extract the finished glass in a plastic state from the pot, the whole is permitted to cool slowly and then broken up with a heavy hammer. The pieces of pot are knocked off the lumps of glass, the useful lumps of clean glass are selected and reheated on the sand-strewn floor of a furnace until they are plastic, and are then pressed either into the form of thick plates or, between suitable moulds, roughly into form of lenses. The material is then annealed, perfect annealing being essential; and this is a slow process owing to the low heat conductivity of glass. Fig. 7 shows four typical pieces of raw glass plate, the largest polished on both sides and two others bearing the original batch number. Since each pot of optical glass has a distinct individuality, and differs appreci- ably from every other pot of glass, the moulded pieces from each pot are stamp- ed with a distinguishing number and their identity is preserved through all the subsequent processes of manufacture. In order to ascertain whether the glass is perfectly annealed and free from bub- bles and dirt inclusions, it is the best practice to grind and polish the plates on both sides and then to view them by transmitted polarized light, as is done by Professor Coker with his celluloid models. Charles Clarke, A.S.C. To Mexico Charles C. Clarke, A. S. C., the Second Vice-President of the American Society of Cinematographers, has been given one of the best photographic assignments of the year. The Metro-Goldwyn-Mayer Studio has assigned Mr. Clarke to direct the photography of “Viva Villa,” starring Wallace Beery and Mona Maris, under the direction of Howard Hawks. This will take Mr. Clarke to Mexico for the next three months. During his absence, Ray June, A. S. C., has been appointed a member of the> Society's- Board of Gover- nors to serve in Mr. Clarke’s stead.