American cinematographer (Jan-Dec 1928)

Twenty-eight AMERICAN C I N E M A T O G R A PHER February, 1928 Tonal values and soft lighting — SECURING the right tonal values and a desirable softness of lighting are more important than ever. Warner Brothers realize this and have made a number of experiments in lighting their Vitaphone films. Result? They discovered that a combination of Cooper Hewitts and incandescent lighting units is necessary to obtain soft tones — whether or not Panchromatic is used. Try Cooper Hewitts mixed with other lamps on Panchromatic, and notice how beautifully you get what you want in tonal values. ^ COOPER HEWITT ELECTRIC CO. HOBOKEN, NEW JERSEY Western Distributing Points KEESE ENGINEERING CO. Hollywood— 7207 Santa Monica Blvd. San Francisco— 77 O'Farrell Street 240 © C. H. E. Co., 1927 On Jan. 1st We Moved to Our New and Larger Building at 7380 Santa Monica Boulevard Hollywood, California Keese Engineering Company Agents Cooper Hewitt Electric Company, Hoboken, N. J. dirt is applied to clean film treated with clean oil, the oil spotting is greatly exaggerated and such dirty oil produces dark spots. A study of the surface structure of motion picture film (see Fig. 2) explains why it is difficult to remove oil by mere wiping. The oil sinks into the innumerable craters present on the surface and can only be removed by treatment with suitable solvents. At the outset it was considered that a waxing treatment might insulate the gelatin surface from the oil and reduce the propensity for oil spots to show on the screen. This was tested as follows: Film toned with an unraium toner was used for the test because such toned film has a maximum propensity to show oil spots, presumably because of the extremely pittel nature of the film surface. A reel of film was assembled consisting of fifty foot strips treated as follows: Sample Nature of Film No. 1 — Plain unarium tone. No. 2 — Waxed with 5% paraffin in carbon tetrachloride. No. 3 — Waxed with 5% solution of 2 parts paraffin and 1 part carnauba. No. 4 — Waxed with 1 % carnauba and overcoated with 5% paraffin. No. 5 — Waxed with 1.5% candelilla and overcoated with 5% paraffin. Preliminary tests to determine the rate of solution of cold waxes and mineral oil indicated that carnauba and candelilla waxes were more impermeable to oil than paraffin, so that in the above double coated tests the object of the first coating of carnauba or candelilla wax was to protect the film against oil, while the coating of paraffin was to secure maximum lubrication. A good grade of light machine oil was splashed in liberal quantities on all the samples while the film was being wound from one reel to another. The film roll v/as then rewound twice during which time the oil was smeared over the surface with a cloth. After this treatment the film surface presented a mottled appearance. The reel was then projected immediately and subsequently three times each day. After the first day objectionable oil spots appeared on the unwaxed sample. At the end of one week no oil spots were visible on any of the waxed samples. It was concluded therefore that paraffin wax although miscible with oil, prevents oil spots. In order to prevent oil spots it is apparently merely necessary to fill up the craterlike depressions on the surface of the film. A roll of toned film treated with candelilla wax and then splashed with oil was prepared over a year ago and projected at frequent intervals up to the present time. No oil spots have appeared on this film to date. 4. The Tendency of Surface Waxed Film to Accumulate Dirst and Develop Scratches on Projection. Sufficient data have not yet been secured to determine the effect of the surface coating on the propensity of the film to accumulate dirt and develop scratches on projection in comparison with untreated film. A projection test was made by applying dirt to the projector gate and by throwing the film on a dirty floor and then projecting. No appreciable difference in the quantity of scratches or dirt accumulated on the film was noticed between surface waxed and edge waxed film. Data in this connection are being secured by circulating reels, half of which are surface waxed and onehalf edge waxed, through various exchanges. 5. The Tendency of Surface Waxed Film to Retain Mositure. It is well known that if the gelatin coating of motion picture film is deprived of its moisture content, the film tends to become brittle. The chief cause of brittleness of projected film is the loss of moisture as a result of repeated baking of the film in the hot projector gate.