KB194849864: Color Pilot - What is the use case of synchronizing an Equinox press profile

Question

When creating a new Equinox profile, one can choose to Synchronize the profile. What is the use case and which option should be used?

Fig. 1

Answer

The synchronization option allows to adjust the dot gain and/ or the gray balance by applying dot gain compensation curves on the measurement data during the creation of an Equinox press profile.

Use case:

In the process of creating an Equinox press profile, some overprint charts are supposed to be printed according to a certain desired printing condition.

That desired printing condition is defined by either an in house printing standard or an industry printing standard. Today, you have two popular industry printing standards, the ISO 12647-2 printing standard (quite popular in Europe) and the G7 calibration method (mainly used in the US region). When choosing the ISO 12647-2 printing standard, you aim for a certain dot gain, while working with the G7 calibration method you aim for a gray balance.

Ideally this desired printing condition (either a target dot gain or target gray balance) is achieved and maintained during the whole print run but in reality you never hit 100% the target. Variations of the printing condition is inevitable (even for a digital press) but you can "flattening" this behavior hardware-wise on the press or software-wise.

Distributing the overprint charts across the press sheet (see fig. 1) and/ or measuring multiple sets of the overprint charts (e.g.: a sample in the beginning, the middle and the end of the print run) is a good method to generate average measurement data.

Fig. 2: multiple copies of overprint charts distributed across the press sheet

While average measurement data is closer to the ideal printing condition, it is still not 100% perfect! But you may ask yourself why it is so important to work with measurement data which is perfect. The reason is simple, you get better results when converting jobs with a profile representing a perfect printing condition!

Let's explain this by the following example. The dot gain in your press profile is equal to the desired printing condition, in this case it is 0% for all inks (linear). The green curve in figure 3 and 4 visualizes this. When converting a job with this profile you get linear output, meaning 50% remains 50% after the conversion. The red curve visualizes the measured dot gain in production of the converted job. Figure 3 shows the dot gain in the beginning of the print run (+10%) while figure 4 shows the dot gain at the end of the print run (-10%). For both situations there is compared with the desired printing condition a dot gain difference of 10%.

Desired printing condition: linear / 0%
Press profile dot gain: linear / 0%
Dot gain in production: +10% at the start, -10% at the end

Let's now use a press profile with a dot gain of +5% for all inks, which is 5% above the desired printing condition (linear). The green curve in figure 5 and 6 visualizes the desired printing condition, the gray curve visualizes the dot gain of the press profile (+5%). When converting a job with this profile the 50% becomes 55% after the conversion. The red curve visualizes the measured dot gain in production of the converted job. Figure 5 shows the dot gain in the beginning of the print run (+10%) while figure 6 shows the dot gain at the end of the print run (-10%). Now there is a different dot gain difference compared to the desired printing condition!

Desired printing condition: linear / 0%
Press profile dot gain: 5%
Dot gain in production: +10% at the start, -10% at the end

Fig. 5: Dot gain in production (start) = +10% Green curve= desired printing condition > linear Gray curve= press profile dot gain > +5% Red curve= measured dot gain in production for 50% > +15%	Fig. 6: Dot gain in production (end) = -10% Green curve= desired printing condition > linear  Gray curve= press profile dot gain > +5%  Red curve= measured dot gain in production for 50% > -5%
50% printed as 65% > Δ = 15%	50% printed as 45% > Δ = 50%

What can we learn from the above example? Working with a press profile which doesn't represent the desired printing condition might result in a less stable printing behavior during the print run compared to working with a press profile in sync with the desired printing condition.

Synchronizing an Equinox press profile

In the "use case" section we explained how to create average measurement data and the benefits of using a press profile in sync with the desired printing condition. Now it's time to explain how to create a press profile which is 100% in sync with the desired printing condition.

When creating a new Equinox profile you have a couple of options to synchronize the profile:

• Don't synchronize the profile: use this option if you want to skip this process.
• Synchronize using standard G7 settings: use this option when using the G7 calibration method for the creation of the press profile.

  • The desired curve will change to G7 for the process inks and to Linear (ΔE-P) for the spot colors.

    What is ΔE-P?

    Please consult Curve Pilot documentation for more information about ΔE-P:
    http://docs.esko.com/docs/en-us/curvepilot/16/userguide/en-us/common/cup/reference/re_cup_measUnits.html

    Synchronize using standard G7 settings

    Desired Curve for CMYK	Desired Curve for spot colors

• Use desired curves from Setup in Curve Pilot Curve Set: use this option when using an in-house or ISO 12647-x printing standard for the creation of the press profile.

  • Select a PressSync curve set having the desired printing condition defined. The desired curves are read from the PressSync curve set!

    How to create a PressSync curve set?

    A PressSync curve set must be created beforehand in Curve Pilot or PressSync Pilot: File > New > PressSync Curve Set.
    Select the correct template based on the used printing standard you plan to use in production. Please consult the Curve Pilot documentation for more information about the template choices: http://docs.esko.com/docs/en-us/curvepilot/16/userguide/en-us/common/cup/reference/re_cup_prsync_intro.html

    Use desired curves from Setup in Curve Pilot Curve Set

    Desired curve for CMYK	Desired curve for spot colors

What you basically define when choosing a synchronize option is the desired printing condition, none, a certain dot gain or the GRACoL gray balance behavior.
Once the synchronize option is chosen, you can proceed with the next steps:

1. Measuring (multiple sets of the overprint charts) or importing the measurement data.
2. Processing the sections:
   1. Create an Averaged Data Set.
   2. Smooth Data.

   3. Synchronize.

      Processing Section "CMYK"

      At this point you synchronize/ match the measurement data with the desired printing condition as specified in the first window when creating a new Equinox press profile.
      You have three methods to synchronize/ match (a desired printing condition):

      1. Tone Measurements only - select this when you've selected the"Use desired curves from Setup in Curve Pilot Curve Set synchronize option.
      2. Mainly Gray Balance Measurements - select this when you've selected the Synchronize using standard G7 settings synchronize option.
      3. Both Tone and Gray Measurements - use this method when the overprint charts were printed using the ISO 12647-x or in-house printing standard but the paper or ink as defined in the standard was not within tolerance.

During the synchronization process the dot gain or gray balance of the measurement data will be modified (synchronized) towards the desired printing condition by applying a dot gain compensation curve. Below is an example of the CMYK and spot color dot gain curves from an Equinox press profile which is and is not synchronized.

Unsynchronized Equinox Press profile	Synchronized Equinox Press profile

A synchronized Equinox press profile is representing 100% the desired printing condition. You could say that this is a profile of an ideal (virtual) printing condition which in practice is not possible to achieve.