Screen E-Book (.PDF) - MacDermid Autotype

We formed our own (subjective) opinionsof the various sequences but werethen fortunate that FESPA Slovakia wereholding a meeting at which Bill Appletonwas speaking. The experienced Slovakianprinters gave their own opinions. Therewas, of course, no agreement about whichsequence was best, though sequence 5and one of the Caza sequences had theirsupporters. Preferences depended, notsurprisingly, on what people were lookingfor. As we will see, the 15° moiré effectstrongly biased many of the judgements.As this effect can be taken into account bya very simple process we will ignore thisaspect of the prints till we come to the sectiondevoted specifically to the effect.Rather than rely on subjectivity, we decidedto create an objective measure whichwe call the Colour Fidelity Index, CFI. Thiscaptures 3 independent factors, all ofwhich have to be right:• Good greys –shifts in greys are a goodindication of a print generally out of control• Good 3-colour tones – this capturesthe fact that a lot of the subjective colourjudgement was based on the more complextones which often looked far toodark.• Good shadows – we want to lose as littleshadow detail as possible.We had anticipated (because of otherwork done at Swansea) using a fourth criterion– the colour gamut. But careful LabThis portion of one of the Linotype-Hell test images shows the widecolour variation from four of the eight test sequences. Clockwisefrom the top left, 4:MCYK, 5:MYCK, 6:YCMK, 8:CMKYmeasurements and plots on the CIE chartshowed that there was no significant differencein gamut in any of the sequences.We have no explanation for why our resultsdiffered from Swansea’s and others mightlike to include gamut in their own CFI.The idea was to obtain objective measuresfor each of these factors, scale each ofthem from 0 100 then divide the total by3 to give us a 0 100 CFI, where 100 is theperfect print.Getting the objective measure for thegreys was easy. For a 20%, 50% and 90%56