ISO 19232-4:2013 gives instructions for the determination of image quality values and image quality tables.

If the IQI requirements specified in ISO 19232‑3 cannot be used because, for example, the absorption coefficients of the IQI material and the inspected material differ by more than 30 %, test exposures are necessary to determine acceptance of image quality values. The image quality values achieved by the test exposures are required for all exposures made under the same radiographic conditions.