American cinematographer (Jan-Oct 1925)

January, 1925 AMERICAN CINEMA TOGRAPHER Twenty-three ently of the kind of emulsion, although tropical temperatures cause more spots to appear especially on positive film. 2. White Spots with Black Centres or Grey Spots with a Black Nucleus and a White Halo. — The most common form is a perfectly round spot, although occasional irregular types were observed as well as group formations of several circular black spots with a large greyish-white halo extending around the entire group. In some cases, the centre is grey instead of black. It was rarely found unless the film had been subjected to tropical temperatures and, in general, the size and number of the markings were greater at the end of one week than after two days under tropical conditions. 3. Black Spots. — Although this marking is by no means as common as some of the the rest of the film, but occurred frequently on each of the different emulsions tested to justify its inclusion in the classification. It appears as a small round spot of density much darker than the surrounding film and of fairly sharp outline, although variations occur wherein the outline is a hazy dark grey halo, darker than the rest of the film, but occurred frequently on positive film, especially if the film was exposed before the moisture treatment, and accompanied by high temperature conditions. In general, the number of markings increased with the time elapsing between the moisture application and development of the film. 4. White Spots with Black Rings. — This marking occurs as a round or irregular white or grey spot with a black or dark grey halo. It resembles a reversal of No. 2. Sometimes the centre of the marking, instead of being clear, contained a small dark spot. The marking was not observed on unexposed film. With both negative emulsions, exposed after the moisture treatment, no markings were found, but on positive film, exposed before the moisture treatment and, especially at tropical temperatures, the spots were very prevalent. 5. 6, 7. Cheese Cloth Impressions. — The usual markings produced by impressing moist cheese cloth on any of the three emulsions consist of a white impression of the fabric on a dark background. The order of exposing has little or no effect on the nature of the marking. At room temperature (No. 5) the impressions are far less accentuated than at tropical temperatures (No. 6). Positive film was slightly more sensitive to the impressions than the Gets Shots that You Couldn't Get at all Without it 4$ u;e I he Ultrastigmat a great deal in commercial work find that I can make interiors with it that would require lights without it, and get outdoor shots on bad days that I could not get without it. (Signed) QUINCY PEACOCK 1611 Market St., Jacksonville. Fla. Write for F older Gundlach-Manhattan Optical Co. 900 Clinton St. ROCHESTER, N. Y. PEACOCK, two negative emulsions. A few cases of black impressions of the cheese cloth were noted on film exposed after the moisture treatment, but the greater number of black markings occurred on film exposed before being impressed with the moist cheese cloth (No. 7). B. Markings Caused by Condensation of Water Vapor from Humid Atmospheres. 8. White Spots. — The most common marking was a tiny white spot similar in appearance to No. 1, except that it was rarely observed in clusters and seldom in sizes over one-sixteenth inch in diameter. At room temperatures few spots appeared unless the film was permitted to humidify for a week, whereas at tropical temperatures the spots were found in large numbers on film left two days in the humidor. When the effect of sudden changes of temperature conditions was studied, very few spots were produced unless the film was subjected to at least eight hour's humidification previous to the change to frigid conditions. In every case the markings were more numerous on film which was flashed before the moisture treatment. When the film was refrigerated previous to humidification, the time of refrigeration had little apparent influence on the size and extent of the markings. 9. Mottled Spots. — On film which had been subjected to sudden temperature changes, irregular mottled spots were found which were of slightly lighter density inside and slightly heavier density outside than the surrounding film. The marking is vague in outline and hazy in appearance. It was occasionally found with a dark grey spot in the centre. In general, mottled spots occurred more frequently