Radiography is a very useful technique for the investigation of the inner structure of old sculptures and bronze statues. In this technique, the photograph must have a wide range of density which corresponds to different thicknesses of the objects. The authors made examinations on the relation between the thickness of test pieces (of bronze and Japanese cypress) and the density of x-ray photograph by changing conditions. The recommended sets of conditions for taking radiographs of bronze objects and wooden objects are: bronze (0 ~ 20mm thick); 260-300 KV, 5 mA, exposure 5 min, distance 120 cm. wooden objects; 40 KV, 5 mA, exposure 2-3 min, distance 300 cm.