The most important index of radiographic quality is the sensitivity of radiography, which is the size of the smallest defect along the direction of ray penetration that can be found on the negative plate quantitatively. Natural defects’ size are hard to be sure. It is obvious that it is unrealistic to use natural defects to evaluate the sensitivity of radiography. Therefore, in order to facilitate the evaluation of photographic quality, it is often used to monitor the image quality of the artificial metal wire, hole, slot, etc. with a certain percentage of the thickness of the inspected workpiece. It should be noted that the sensitivity of image quality indicator is not equal to that of natural defects. However, if the sensitivity of image quality indicator is improved, the sensitivity of natural defects will also be improved.
