The national standard densitometer can be used for calibrating photographic film and visual photo. The development of biomedical image and space technology need large measurement range and high uncertainty of visual density. A newly designed equipment using hemispherical emitter with optic fiber can enhance the diffuse coefficient of the light to 0.945 which is higher than the other national standards (0.02-0.03). Thus the measurement range can be increased to 0-6.0 and the combined uncertainties are 0.0015 (0 D D < 6.0). On the other hand, the structure design for the whole equipment can realize the reciprocal fixing between the light module and the detect module. So the validity of Helmholtz reciprocity for transmittance measurement can be examined and proved on this new equipment.