Abstract: The D(log E) curve of an unknown film is obtained by first measuring a first film having a known D(log E) curve and of the same type as the unknown film. Measured are the densities of a plurality of objects and their corresponding distances for which the object densities decay to film base densities. These values are plotted and with the known D(log E) curve, an x(log E) curve is obtained which is valid for all films of this type. The unknown film is measured to obtain values of object densities and corresponding decay distances and a curve of the values is obtained, and when used with the x(log E) curve for the film type, a new D(log E) curve is obtained for the unknown film.

Abstract: The present invention discloses an analysis procedure which permits the calibration of airborne thermal infrared systems to absolute ground temperature and the removal of variations due to slant angle without the need for ground measurements. Absolute ground temperature are extrapolated from data taken at a plurality of altitudes over a selected reference point.