Document Type : Research Paper

Author

• Gholamreza Delafkaraan

Surveying Flights Engineer

Abstract

Up to ten years ago, when talking about selecting an airplane for shooting, we were looking for features such as: good standing power, large wing, vast operating range and, most importantly, low or medium speed. The low speed of the shooting aircraft was favorable in the sense that, when the camera’s light valve was opened, the stretch of the features across the surface of the image, caused by the forward movement of the aircraft, be kept as small as possible, not exceeding 25 microns. This would prevent the selection and use of films whose sensitive layers had greater power of recording or resolution, because the speed of recording of these films is very low due to small-grained crystals in their emulsion, and must therefore be exposed to light for longer periods of time. In order to avoid the elongation of the image, a low-speed aircraft and fast films (with large-grained crystal and low resolution) were used to provide a good image in a very short time through receiving proper amount of light.