Problems involving density measurement in aerial photographs

Density values obtained by the use of different density measuring devices employed in conjunction with several types of film which have different diffusion characteristics are compared, and it is concluded that one calibrated gray step wedge does not suffice for the adjustment of instruments used to determine density measurements in aerial photographs. Each film type is found to require a calibrated wedge of the same material. The problem of establishing international standards in the field of density measurement is examined, and the characteristics of diffuse density, specular density, and double diffuse density are considered.