Warning: You should make sure to create a copy of your data record before you modify its curves. If you do not, you run the risk of losing your original data irrevocably by modifying them.
1.List box below "Curve Modification": Select the edit or correction function you want:
•"Modification of Measurement Values"
•"Correction of Process Deviation"
•"Modification of Calibration Curve"
•"Correction of Gray Balance".
See below for a description.
2.The list box is enabled when you check the box to its left. Afterwards, the "Modify%" column displays as well in the table and you can edit it. The modification values that display depend on the edit function you selected.
Three curves display:
•In the color concerned: Modified data curve or calibration curve
•Green: Curves showing modification values
•Orange: Original curve
3.Click "Modify" to apply the change.
Remove the tick from the check box if you do not wish to apply the change.
List box => "Modification of Measurement Values"
This edit function lets you, for example, apply the calibration of one print route to a second one if the differences in dot gain are known for both routes.
Example: You have two print routes with two different presses. Let's also assume that you know that the dot gain in output on the second route is always 5% higher than that on the first route.
In this case, it is enough to measure the dot gains of the first route and to create a data curve from them. You can obtain the data curve for calibration of the second route by modifying the data curve of the first route. In this example, a modified curve that increases the measured values by 5% in the midtone would be used.
List box => "Correction of Process Deviation"
This function allows you to correct a process calibration that did not come up to the calibration target (i.e. the prescribed dot gain) defined by the process curve set.
Example: The process curve set for a process calibration defines (for cyan) a dot gain of 15% for the nominal value of 50%. In print, however, you have 18% dot gain for cyan. In other words, a dot percentage of 68% is measured for the nominal value of 50% on the calibrated test chart. This gives you a process deviation of +3%.
You can now modify the measured process calibration data used for calibration so that the deviation of +3% is corrected. A correction value of -3% is used for the nominal value of 50%, i.e. dot gain is to be reduced by 3% for 50%. Take note that a negative correction value results in greater measurement data and, consequently, to lower values of the calibration curve.
You must enter a correction value of '-3' in the "Modify%" column if the "Correction Values" radio button is enabled.
You must enter a correction value of '68' in the "Modify%" column if the "Measured Values" radio button is enabled.
In the latter case, you do not have to calculate the correction value as described above.
•"Import Minispot": Import of the measured data of a minispot from an IT8 file. The modification values required for correction are computed automatically based on these data and on the process values. See also Minispot Import.
List box => "Modification of Calibration Curve"
This function allows you to raise or flatten the curve directly. It is often very difficult to gage the impact that a modified calibration curve has. For this reason, this edit function is recommended only for very experienced users.
Note: Remember that, for technical reasons, there are limits to the modifications you can make. For that reason, it's important that you compare the modified calibration curve with the original curve. This is best done by displaying the calibration curve and its values.
List box => "Correction of Gray Balance"
This correction function is available only for calibration data records with CMYK and a separate calibration. (A separate calibration means that each color has its own calibration curve, see also the Overview of Averaging Data Curves.)
A correct dot gain does not necessarily produce an optimal gray in the overprint of CMY (see also the Diagram => Spread as displayed in a graph.)
The gray balance correction that you can use in this function enables gray to be optimized based on the gray minispot.
The aim is:
•The dot gains in all the CMY curves continue to be within the tolerance range (see the Diagram => Tolerance as displayed in a graph).
•The dot gains of CMY are balanced in their ratio to one another so that an optimal gray results.
Gray balance minispots are placed on the press sheet for gray balance correction. These gray minispots are evaluated with the Profile Tool in the Prinect Color Toolbox. The result is an IT8 file with gray balance correction data.
The "Correction of Gray Balance" function enables this IT8 file to be imported. The gray balance is then corrected in the Calibration Manager. In this process, existing calibration curves are replaced by curves that lead to a correct gray balance.