The more patches, i.e. color fields, a test chart has, the more accurate it is. When creating the test charts, a number of 418 patches (19 rows of 22 columns each) was used, since this makes optimal use of an A4 sheet. This results, in theory, in a medium sized spectral data set. Of course, it would be possible to work with a larger spectral data set (e.g. 836 fields), but this requires longer times in the spectral data measurement by the spectral measuring device. In addition, the test result may become inaccurate due to the inaccuracy of the risograph. Finally, it is unknown to what extent the risograph varies in reproducing the colours to achieve a reliable measurement result. This individuality within each original underlines the craftsmanship of the risograph.