Abstract: The situations, theoretical background, particular rules have been specified in ISO 17636-2:2013. In fact, the formula of theoretical background of compensation is just a change of the formula of object contrast in radiography. The particular rules are based on the effect of the unsharpness upon the contrast of the detail radiographic imaging. It must be understood that the function of compensation rules is to achieve a sufficient contrast sensitivity of imaging. When using compensation rules,it must take the characteristic of defect in correpondence with the material,technology and structure of product into account,and it must also take the specification requirements of product into account.