| OCR Text |
Show 14 B. Transferring Information from the Photographs The second general source of difficulties connected with the preparation of accurate maps from serial photographs steins from the several procedures involved in making measure-ments on the original photographs, or negatives, and in trans-ferring quantitative information from the photographs to the map-compilation sheet. Some oZ the operations which can and do frequently entail dif f i cu.lcies at this stage of the photo-grammetrie process are: 1. Developing the original negative films or plates. 2. Making positive prints from the negative films or plates. 3. Operating the photogrammetric plotting instruments. (Which correct for parallax, tilt, etc.) The processing or developing of the original negative films or plates, particularly films, is an extremely critical operation, and requires meticulous care, thorough workmanship, proper equipment, and professional skill. The original efforts are wasted if the film.-! are later carelessly processed and improperly developed. Not only must the chemical treatments be applied properly to bring out the maximum in image quality and to prevent "creeping of emulsion," but it is equally important that the film base be handled carefully and properly in ordex to reduce to a minimum the expansion, shrinkage, stretching, warping, curling, and even tearing of this material.2' |
