In order to establish a quantitative relationship between the gray scale density of films in model DGP-ⅡA multispectral band camera and the radiance of terrain subjects imaged on the film

we fabricated and calibrated a group of simple radiance-meters corresponding to the 4-spectral bands of the camera. When taking the photographs of the standard ground subjects

we at the same time measured their radiations for each band by means of the radiance-meters

then calculated the radiance of the ground subjects corresponding to the film density and calibrated the gray scale of the films with considerations of the spectral response of the films and the transmittance of the filters.