Flying over Cambridge in zero weather, handling a camera weighing over 100 pounds, taking pictures of the Stadium and the Houses; then returning to develop and print their negatives in the Geographical building--all this is just in the day's work for the Harvard student who takes "Geography 36," the course in Aerial Photography given by the Geographical department. Four United States Army officers, all connected with Wright Field, in Dayton, Ohio, and representing the Air and Engineering Corps, have charge of this unique course, presented in the second half-year.
The idea of the course is to give both theoretical and practical knowledge in the field of aerial photography, with the added thrill of really flying. Lectures are given on four phases of the work, and this theoretical knowledge is then made use of in actual photographing. Captain Albert W. Stevens, of the Air Corps, will give the first series of talks on the chemistry of developing and printing the negatives; from there, the embryo fliers will advance to the interpretation of photographs taken from the air. To an inexperienced observer, aerial photographs are either wholly or partly unintelligible; so to correct this condition, Captain Dache M. Reeves, also of the Air Corps, will demonstrate and explain the method of correctly interpreting the pictures. The mathematical side, involving the computation of scales and altitudes, will be presented by Captain Bruce C. Hill, who is of the Engineering Corps, while First Lieutenant James F. Phillips, another Engineer, will instruct the men in practical application in the laboratory and in the air.
Last year, this course was somewhat handicapped by the lack of adequate laboratory equipment, which was not installed until late in the spring. For its size, this laboratory is one of the most thoroughly equipped aerial photography laboratories in the United States. It consists of seven rooms in the basement of the Geographical building. Two of these are used for the restitution of photographs taken with the 5-lens camera; four are given over to the processes of developing, printing, and enlarging, as well as for copying mosaics; and the last room is used for loading the cameras. This room is absolutely light proof, and without illumination of any sort, since aerial films are sensitive to all wave-lengths of light; that is, they are pan-chromatic. Even a green safety lamp cannot be used; all work is done by the touch system.
One of the cameras used in the course is equipped with five lenses, and weighs about 105 pounds; however, one man has no difficulty in handling it. This 5-lens camera has been found to be the best machine for taking photographs of large areas with the minimum amount of flying and using the minimum amount of film. Its range is approximately one mile for every 1000 feet of altitude; that is, if the plane were flying at 27,000 feet, the negative would represent an area measuring 27 miles each way. It is in the finishing of this negative that the restitution printer is used. If a print were made directly from the negative, the finished product would give the appearance of an inclined plane. However, the negative is placed in the printer at such an angle that the final photograph, which is shaped like a Maltese cross, gives the same scale on the wing photographs as in the center. The Germans have tried a camera with nine lenses, in connection with this work, but due to the short focal length, the scale is rather small, and the results not so good.