Dear DarkoT, your question is just wrong. In NDT we are doing testing and NOT measurements. Therefore, our image quality indicators we are using to confirm the achieved image quality according to ISO 19232 do have a statement of conformity from the manufacturer only. This statement, that the IQI corresponds to ISO 19232, is suffucient and does NOT expire. We at BAM offered for decades a certification program for certification of image quality indicators, but nobody signed a contract in this program. So recently, caused by focus sharpening, we deleted this program without any customer from our portfolio. A calibration is only necessary if you do measurements and you are an accredited measurement lab according to ISO 17025 or similar. Than your measurement equipment should be traced back to nomal unit representations, in the case of the meter unit it should traced back to the Si-unit representation by NIST or German PTB. To my knowlegde there exists no calibration lab, which is able or willing to calibrate any ISO 19232 IQI, therefore there is also no need to re-calibrate any IQI. Please do not mix requirement of testing with requirements of measuring. There is NO uncertainty in Non-Destructive Testing! Uwe Z.