Calibration matching

This page applies to Harlequin v13.1r0 and later; both Harlequin Core and Harlequin MultiRIP.

This section describes how the RIP uses the /WarningsCriteria dictionaries to select the most suitable calibration set sub-dictionary for the object and colorant concerned, from a calibration group.

First of all, any calibration set sub-dictionaries whose /WarningsCriteria dictionaries contain any entries whose values conflict with those for the current object and colorant channel are eliminated.

For example, if we were using the following calibration dictionary (which has rather simplistic calibration and colorant sub-dictionaries), and were calibrating (at any page resolution) for an object which used a Line screen for the colorant channel concerned, the first 4 calibration sub-dictionaries would be eliminated from consideration, and we would use the last one which has a /HalftoneName of /Line in its /WarningsCriteria sub-dictionary.

            <<
            /CalibrationType 6
            /MissingCalibrationAbort false
            /ActualPress[
              <<
              % Compensate for dot gain at 50% by calibrating to 40%
              /WarningsCriteria << /HalftoneName /Euclidean >>
              /Default << /CalibrationType 2 /Curve [ 0.0 0.0 0.5 0.6 1.0 1.0 ] >>
              >>
              <<
              % Compensate for dot gain at 50% by calibrating to 40%
              /WarningsCriteria
              <<
              /HalftoneName /Round
              /Frequency [30 80]
              >>
              /Default << /CalibrationType 2 /Curve [ 0.0 0.0 0.5 0.6 1.0 1.0 ] >>
            >>
              <<
              % Compensate for dot gain at 50% by calibrating to 30%
              /WarningsCriteria
              <<
              /HalftoneName /Round
              /HWResolution [600 600]
              >>
              /Default << /CalibrationType 2 /Curve [ 0.0 0.0 0.5 0.7 1.0 1.0 ] >>
            >>
              <<
              % Compensate for dot gain at 50% by calibrating to 40%
              % and for dot gain at 40% by calibrating to 30%
              /WarningsCriteria << /HalftoneName /Round >>
              /Default << /CalibrationType 2 /Curve [ 0.0 0.0 0.5 0.6 0.6 0.7 1.0 1.0 ] >>
              >>
              <<
              % Compensate for dot gain at 50% by amounts that vary per channel
              /WarningsCriteria << /HalftoneName /Line >>
              /Cyan << /CalibrationType 2 /Curve [ 0.0 0.0 0.5 0.8 1.0 1.0 ] >>
              /Magenta << /CalibrationType 2 /Curve [ 0.0 0.0 0.5 0.2 1.0 1.0 ] >>
              /Yellow << /CalibrationType 2 /Curve [ 0.0 0.0 0.5 0.2 1.0 1.0 ] >>
              /Black << /CalibrationType 2 /Curve [ 0.0 0.0 0.5 0.1 1.0 1.0 ] >>
              >>
            ]
            >>

If, however, we were printing at a page resolution of 300 dpi and the object concerned was using a Round screen with a screen frequency of 100 lpi for a particular colorant channel, we would use the 4th calibration sub-dictionary for that colorant as it would be the only one not to be eliminated on the basis of the /HalftoneName, /Frequency or /HWResolution entries in its /WarningsCriteria sub-dictionary.

In the two cases above we were left with only a single calibration sub-dictionary. But if we still have several to choose from then, calibration set sub-dictionaries whose /WarningsCriteria dictionaries are not specific about the circumstances to which they apply are eliminated in favor of those which apply to specific conditions. Some criteria are weighted more heavily than others for this. The order of importance of criteria, (from most to least important) is:

HWResolution, HalftoneName, Frequency, NegativePrint, Exposure.

So, looking again at the calibration dictionary above, if the page resolution were 600 dpi and we were calibrating for an object and colorant channel using a Round screen with a screen frequency of 50 lpi, then having already eliminated the two calibration set sub-dictionaries that are not for a /Round screen, we would select the 2^nd of the 3 calibration sets that are for /Round screens as it is more specific than the 3^rd one which is for any page resolution, and although the first two calibration set sub-dictionaries for Round screens are both specific about two items, the /HWResolution is weighed more heavily for this than the screen /Frequency.

Lastly, if having done this, if there is still more than one calibration set sub-dictionary to choose from, priority is given to a calibration set which contains a specific entry for the colorant concerned over one where the /Default entry would be used for that colorant. Lastly, if no decision is made a calibration set sub-dictionary with a /CalibrationName earlier in the alphabet is chosen, or failing that the earlier one in the PostScript language array representing the calibration group.