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Print Workflow using a G7 Linearization

The output result when printing the same file on different machines does not look identical. To achieve identical results the input data has to be converted using a color management system.

 

Complete Conversion Chain

The complete conversion chain typically consists of the following steps:

Press Preset

The press is brought into conditions deemed ideal by the manufacturer.
This step typically involves these parameters:

Ink setup

The maximum amount of ink per channel and in total is set

Uniformity correction

The system is adjusted to achieve equal color across the print format

Pre-Linearization

The system is adjusted in a way that the tone values follow a known curve

Linearization

In order to assure smooth gradations and a predictable output of tone values the system is adjusted to follow known tone value curves.
This is a 1-dimensional per-channel adjustment.

MYIROtools can calculate the correction curves to adjust a press to the G7-specification.

ColorSpace Conversion

The tone values of input files are converted to the printing systems output color gamut.
By this the device dependent tone values (e.g. CMYK) are converted to tone values that produce the correct colors when printed using your printing system. This is typically done using the source profile embedded in the files (or preset in the DFE) and the printer profile (the profile describing your printing system).

ColorSpace Conversion

ICC Profile Conversion

The color conversion is typically done using ICC-Profiles which are used to perform a conversion from input device data (such as RGB) to output device data (such as CMYK) using a translation color space. This translation space is usually CIELAB and known as PCS (Profile Connection Space).

In todays print workflows digital input files such as PDF files are converted in systems called a RIP, DFE (Digital Front End), Controller or similar.  To achieve good conversion speeds the accuracy is often limited to 8Bit. This limitation is not a problem in practice if the machine is brought into a "linear" state. Thanks to this linearization the necessary corrections to achieve accurate color output is minimized and the available 256 steps per channel (8 Bit) are enough.

 

Linearisation

Such a linearization can be done using various methods. All of them have one thing in common: They have to be applied at some point during the whole conversion chain from input to printed product.

Here we explain two typical scenarios using the G7-methodology as an example.

Method 1.
G7 Curves applied in Controller

MYIROtools generates one correction curve per output channel. These curves are used to make sure that the output of the press before any color conversion is applied meets the requirements of the G7-methodology.
The curves can be loaded into the controller of many types of printing machines.

Method 2.
G7 Curves applied as DeviceLink

MYIROtools generates one correction curve per output channel and saves these curves as CMYK2CMYK DeviceLink Profile. This DeviceLink-Profile can be used if the Controller is not capable of applying linearization curves.

Method 1

Workflow to apply G7 curves in the controller

This workflow uses paper dependent set of curves but is independent from the source of the data

Step 1
Step 1
Start the G7 Press Setup Workflow and select "Create G7 linearization". Then click "Next".
Step 2
Step 2
In the next step you need to measure the P2P51 chart. You can open it through the workflow and print it or use a chart that you've already printed. Make sure to have all color conversions switched off and only the standard curves (usually linear) applied.
Step 3
Step 3
After the measurement is completed select the appropriate measurement condition (usually M1) and click "Next"
Step 4
Step 4
Choose a name and a storage location for your G7-correction. MYIROtools will save a correction DeviceLink ICC-Profile and a .csv-file containing the correction values.
Step 5
Step 5
Enter the values from the .csv-file in the linearization dialogue of your DFE. Please refer to the user manual of the DFE to select the correct interface.
Step 6
Step 6
The G7-Linearization is now finished. You can continue creating a press profile. For a digital printing machine it is necessary to create a profile. For an offset press you are finished and can accept data that was prepared using a CRPC for the paper you are using for production.
Method 2

Workflow to apply G7 curves as DeviceLink Profile

This workflow uses dedicated DeviceLink Profiles for every conversion.
For example:
G7_DVL_CRPC6 – MyMachine_Paper1.icc
G7_DVL_CRPC3 – MyMachine_Paper1.icc
G7_DVL_CRPC6 – MyMachine_Paper2.icc
G7_DVL_CRPC3 – MyMachine_Paper2.icc

Step 1
Step 1
Start the G7 Press Setup Workflow and select "Create G7 linearization". Then click "Next".
Step 2
Step 2
In the next step you need to measure the P2P51 chart. You can open it through the workflow and print it or use a chart that you've already printed. Make sure to have all color conversions switched off and only the standard curves (usually linear) applied.
Step 3
Step 3
After the measurement is completed select the appropriate measurement condition (usually M1) and click "Next"
Step 4
Step 4
Choose a name and a storage location for your G7-correction. MYIROtools will save a correction DeviceLink ICC-Profile and a .csv-file containing the correction values.
Step 5
Step 5
To use the G7 DeviceLink it is necessary to "bake" it into the complete color conversion. Therefore the next step is the creation of a color space conversion (CSC) DeviceLink Profile.
Step 6
Step 6
In the process you can choose from four different presets. 1) Digital Production Printing Suitable for any production printing process where a CMYK reference should be achieved 2) LFP Production Obtains more vivid results 3) Simulation Mainly for proofing purposes 4) RGB Production Use if the source data is RGB
Step 7
Step 7
When asked choose an appropriate name for your color space conversion profile.
Step 8
Step 8
Now the G7 Correction needs to be linked with the color space conversion. This is called "concatenation"
Step 9
Step 9
Select the color space conversion DeviceLink created in the previous step as first (source) profile. Then select the G7 correction profile as second (destination) profile. Choose a meaningful name and save the profile.
Step 10
Step 10
The profile we've just created contains the full conversion from source to destination to linearization. This could be e.g.: CRPC6.icc - MyMachines_Output_Profile.icc - G7Correction_for_my_machine.icc For other source profiles you need to create another concatenation.