For process control during proof and production printing, a multi-colour strip shall be printed along with the subject. It shall contain well-defined control patches with accurate tone value designation and meet the film quality requirements of 4.2.1 Futher, the shape of the halt-tone dots should be circular, the screen ruling shall be 30 cm. The tone value ranges shall be at least those given in Table 5. For non-periodic screen, the minimum dot diameter should be 50. If a digital control strip is exposed on film, together with the subject matter, the control patches should be inspected on film to ensure that the intended tone value and the requirements of this subclause have been achieved.