The Moving Picture World (May 1907)

134 THE MOVING PICTURE WORLD. Projection Lenses. For the Nickelodeon. • : ~ ■ By The Editor. Referring to our issue No. 4, March 30, and the table of distances, several correspondents have written that they cannot get the size disc as mentioned with Darlot lenses. The ie uses mostly in use in England, where these tables have been in use for the past fifteen to twenty years, are cylinder lens of English and French make, on which is engraved their focal length, and if these are used there should be no difficulty in using the tables. When exhibiting for the Gilchrist and University lectures-, in halls varying from 50 to 150 feet distance from screen, we relied absolutely on the tables and they never failed us. For the benefit of our readers we are now making ex- periments with Darlot lenses and will shortly publish the results, and if necessary prepare a new set of tables for their use. In the meantime, if readers will find the focus of their lens by holding front of same pointing towards a window and get a sharply defined image on a piece of paper pinned to wall, then measure from paper to mid- way of lens mount, they will get the focus of lens. Do not. use the back focus as a guide or it will cause difficulties; for instance, if the back focus is 12 inches and the front focus 9 inches, the equivalent focus of the lens should be between 8 and 9 inches, and if our readers will bear this in mind when using these lenses their troubles will vanish. We have pleasure in reproducing a reference table we prepared for cinematograph lenses. This table is worked out on similar lines to the lantern lenses, and from several tests we have made it is approximately accurate. The following figures will interest those owners. 4 Nickelodeons who have one or more competitors an complain because there is not variety of film subject enough to supply a number of theaters situated near eaci other without repetition or duplication of subject; tfe figures are approximate, and do not include an occasional subject imported from an irregular source of supply, There were placed upon the American market new fib subjects: In November, 1906, total number of feet 10,00 In December, 1906, total number of feet n^oo In January, 1907, total number of feet....... 12,00 In February, 1907, total number of feet 14/xx In March, 1907, total number of feet 28,00 An analysis of these figures means that the availabl number of reels of new film subjects increased from ta in November, 1906, to twenty-eight in March, 1907. Tm Nickelodeons located in one block, changing reels thre times weekly, each using new subjects only, were force to show the same pictures more than half the time November, 1906, while in March there was no need duplicating at any time.' The representative of a moving picture manufacture received this-week the following: "Enclosed please find $6.50 and a photograph of mysd and band. Please send me quick as possible a 50-foc moving picture of the band and oblige."— So Saj Variety. Distance between Cinematograph and Screen. 10. feet 12 " IS " 20 " 25 '*-■ SO " 35 " 40 " 45 " 50 " i 75 "■ 100 .« - 150 " •/ ■•• 2 in. READY REFERENCE TABLE DISTANCES FOR CINEMATOGRAPH LENSES. FOCUS OF LENS. 2% in. 2% in. 3 in. 314 in. 3^ in. • • 4 m. 5 m. ft. in. 5 o DIAMETER OF PICTURE (obtained with i-inch mask). 6 7 10 o 12 6 J50 17 6 20 o 22 6 25 27 49 o 6 o 6 6 73 6 ft in. 4 O 49 60 80 10 o 12 O 14 O 16 O 18 O 20 O 30 O 40 O 60 o ft in. 36 44 56 7 3 90 it o 12 8 14 6 16 4 18 4 27 8 37o 55 4 ft in. 3 4 40 50 6B .84 10 o 11 8 13 4 150 169 25 1 33 5 50 1 ft in. 3 2 39 48 62 79 93 io 7 9 12 4 14 o 15 6 23 3 3 1 o. 466 ft in. ft in. 2 8 m 46 58 7^ 86 10 o 11 6 130 14 3 21 5 28 7' 42 ii -■ o 3 S" 50 60 70 88 98 ii o 11 9 17 6 239 35 9 ft in. 2 O 26 30 46 5 10 62 7 8 92 10 o 150 20 o 30 b 6in. ft in. 14 18 20 34 38 40 48 5" 70 78 114 150 22 41