Amateur Movie Makers (Dec 1926-Dec 1927)

EXPOSURE DATA for Fall and Winter HE correct exposure of film is the amateur's assurance that he will get a photographically good picture on the screen. There is a certain "leeway" allowed in calculating exposure. This is known as the "latitude" of the film. For example, if the latitude of a film, on a certain exposure, is between the diaphragm stops of F:5.6 and F:ll, these stops and all those intermediate will register a certain kind of image on the emulsion. Below and above those points will be over-exposure and under-exposure respectively. But as we approach the limits of this latitude our film becomes poorer in quality. There is a certain point within these limits, however, at which the exposure is absolutely correct. A picture made with the exposure dial set at this point is always excellent in quality. Where the scale of contrasts in a subject is very abrupt, and extended, the latitude of our film is very narrow. With a more compressed scale of values from black to white, the latitude increases, and we are allowed more freedom in setting of diaphragm stop. If you are using film that is to be reversed, be careful of over-exposure. The old rule of exposing for the shadows and letting the high-lights take care of themselves does not hold true in this case. Over-exposure with reversible film gives a weak, washy film with much grain. When using negative film, which is to be printed to a positive, the old rule applies, over-exposure yielding a much better print than underexposure. Under-exposure with a negative means that the print has to be forced in the developer, which greatly increases the grain. In calculating exposure, the following factors should be taken into consideration : (1). Actinic Value of Sun's Light — (a) When the sun is shining brightly with no haze or dust present in the atmosphere, a certain diaphragm stop is used. Light clouds present in the sky when the sun is strong do not necessarily mean that the diaphragm stop must be changed. They often intensify the light by reflecting it. (b) The diaphragm stop must be opened wider when the sun is obscured by clouds. By Walter D. Kerst (c) When it is very dull and cloudy, the stop must be opened still wider to compensate for the loss of light. (2). Diaphragm Stop — The diaphragm controls the amount of light which reaches the film. The stops usually marked are F:3.5, 4, 5.6, 8, 11, and 16. Each succeeding number gives one-half the exposure of the one preceding. (3). Time of Year — For all general purpose, the year can be divided into two parts when the light condition varies, from April to September and October to May. (4). Time of Day — Between the hours of 8.30 and 4.30 the sun's light value can be taken as about the same. Earlier or later than that the diaphragm stop should be changed to compensate for the weaker light. (5). Latitude — Sunlight varies as one goes further north or south of the equator. This factor must be taken into consideration when shooting. (6). Altitude — When shooting at altitudes above 5000 feet, the diaphragm must be stopped down to compensate for the increased power of the sun. For above altitudes of 5000 feet, give two-thirds less exposure than normal; above 10,000 feet, one-half less normal. (7) . Nature and Color of Subject Photographed — Distant landscapes require a shorter exposure than subjects nearer the camera, the exposure increasing with the nearness of the subject. A normal shot of a white house surrounded by trees would fall in the same exposure cla=s as one of a red house in similar surroundings. However, less exposure is given the white house because of increaced reflection of light from subiect, and because of the poor actinic value of the red house. This holds true of other subjects in other exposure classifications. (8). Environment of Subject — A figure in an open field takes less exposure than one under the shade of trees. A boat out on open water takes less exposure than one on a river whose banks are heavily lined with trees. The following classifications with their appropriate exposures are illustrated on the next page by one example from each class, the first one listed in each class having been chosen in each case. Study of the subjects with the example illustrated will enable the amateur to judge in what classification the subject he is photographing belongs. This exposure guide is for use from October to May inclusive, between latitudes 40 and 45 degrees, north, in any part of the world. CLASS 1. 1. Clouds only. 2. Sea only. 3. Expanse of water only. Exposure. Bright Sun. F:16 with 2X filter. Cloudy. Set pointer between F:16 and F:ll with 2X filter. Dull Cloudy. Set pointer between F:8 and F:ll. CLASS 2. 1. Glaciers only. 2. Snow only. 3. Aeroplanes in sky. 4. Any small objects in sky such as birds, kites, etc. Exposure. Bright Sun. F:ll with 2x filter. Cloudy. Set pointer between F:16 and F:ll. Dull Cloudy. F:8. CLASS 3. 1. Distant landscapes. 2. Snow scenes with dark small objects. 3. Boats out on open water (sea scenes, objects 100 feet or nearer). 4. Objects on boats not casting heavy shadows. 5. Scenes on beaches. 6. Sky at sunrise or sunset. Exposure. Bright Sun. Set pointer between F:ll and F:16. Cloudy. F:ll. Dull Cloudy. Set pointer between F:8 and F:5.6. CLASS 4. 1. Athletic sports in the open. 2. Closeups of class 3. 3. Peoples, etc., in the open, nothing to obstruct the light. 4. Open landscapes: (objects at less than 200 feet when foreground is unimportant). 5. People and objects near water, no heavy shadows. 6. Buildings light in color. 7. River scenes, no obstruction of light. Exposure. Bright Sun. Set pointer between F:ll and F:8. Cloudy. F:5.6. Full Cloudy. F:4. CLASS 5. 1. Any landscape with dark foreground in shadow. 2. Closeups of class 4. 3. Groups in garden, partial obstruction of light by trees. 4. Scenes on well-lighted porches. 5. Buildings dark in color. (Continued on page 64) Twenty-three