ZePrA | Job Warnings

Job Warnings

Customize job warnings for configurations

Customize Job Warnings for Configurations

In general, job warnings and error messages will be issued when problems or errors occur while processing a file. Files with a yellow warning in the Overview window have been processed but may have issues. They are placed in the Output Folder. Alternatively, when configuring the Queue, define an Output Folder with Warnings, where such files will be moved after processing. Incorrectly processed files, fatal errors or unsupported file types are highlighted in red and are moved to the Error Folder.

The list contains all existing warning messages. Their behavior can be customized independently for any configuration, for example if you don’t want a warning message for a certain problem or if you feel that a problem is so serious that it should better be treated like an error.

Note: The behavior of error messages can’t be changed.

Job Warnings can be adjusted individually: Right click on the desired job warning to open the context menu. Select Inactive, Active or Active (Treat as Error).

Inactive: Deactivates the job warning in the selected configuration. The Overview window no longer displays a yellow warning.

Active: Activates the job warning in the selected configuration.

Active (Treat as Error): Treats the associated problem like an error. The file will be highlighted in red and moved to the Error Folder.

Reset: Resets the changed warnings to the default settings.

ZePrA | Applying Correction DeviceLinks

Apply Correction DeviceLink profiles

Apply Correction DeviceLink Profile

The more reliable the color behavior of your printing machine is and the more accurately the corresponding ICC profile maps the printing process, the better the color conversion via ZePrA will be. In practice, however, it is often very different. Variations between the batches of paper, other dot gains or fresh inks that differ from the last series used can result in tonal shifts and deviations in the distribution of tonal values.

CoPrA SP* and the Update Profile module is integrated in the SmartLink module of ZePrA in order to compensate for these variations and deviations. Instead of having to generate a completely new printing machine profile and DeviceLink profiles for such deviations, the Update Profile makes the required adjustments. To ensure your printing machine prints the same color appearance as before, just a few details are required, such as the spectral measurements of dot gain strips or better still, the Reprofiler measuring strips that we provide with CoPrA.

The Correction DeviceLink profile will be applied after the color conversion defined in your configuration. So, you can continue to use your tried and tested DeviceLink profiles without having to replace them because of a change in the target color space of your printing machine.

Note: *SP = Serialized Profiles. The profiles created with CoPrA SP are encoded with the serial no. of the ZePrA color server and can only be used there.

Preparations for using the Updating Profile function

CoPrA’s Update Profile tool allows adjustments of an existing profile with just a few color measurements quickly and easily. Optionally a Correction DeviceLink profile to be applied in ZePrA can be created. Note that such profiles can only be used in ZePrA versions 4.6.2 and higher.

  1. Two types of Reprofiler control strips for different measuring instruments are included in the scope of delivery for both CMYK and RGB-based printing systems. For other color spaces use ColorAnt to create Reprofiler control strips.
    • The small control strip is available as a one-row and a two-row strip. The one-row strip can easily be integrated in the trim area of your printing machine.The two-row strip is more suitable for digital printing or inkjet systems.
    • The same applies for the large control strip, which contains significantly more color patches and is thus more suitable for optimizing relatively large color deviations.

      Note: In principle, you can not only print and measure the ColorLogic control strips, but also other measuring strips, such as Ugra/Fogra, IDEAlliance Media Wedge, ECI GrayControl Strip, ECI bvdm TVI or UGRA UDKS Wedge, are supported too. Alternatively, you can use an existing measurement file that reproduces your current printing conditions.

  2. Once you have printed a control strip, measure it using a spectrophotometer.
  3. Make sure the color management settings are deactivated upon output of the control strip, i.e. without simulation of a printing condition for example. This is especially the case for digital printing systems.
  4. The Update Profile in CoPrA optimizes the ICC profile of your output profile (= printer profile that was selected in ZePrA as the Target Color Space).

Procedure in ZePrA

  1. In Configuration, Document/Target click the checkbox Apply correction DeviceLink profile. If there are no correction DeviceLink profiles, the option for Correction is completely grayed out.
  2. Click Settings to open the Correction DeviceLink Profile dialog and select a correction DeviceLink that has previously been created with CoPrA.
  3. We recommend that you not only select the Correction DeviceLink profile, but that you also embed the associated updated target profile into the converted files (Embed updated Target Profile instead of the Target Profile). When this option is enabled, this profile becomes the new output intent of a converted PDF file. The updated target profile is shown below.

    Note: ZePrA checks whether there are corresponding correction DeviceLink profiles and updated printer profiles for the selected Target Color Space. These profiles will be shown and can be selected once the Apply correction DeviceLink profile has been enabled.

ZePrA | Spot color processing

Spot Color Processing

ColorLogic’s spot color solution is aimed at printers whose customers impose stringent demands on the color accurate rendering of spot colors. Packaging printer that process files with many different spot colors looking to optimize their printing process by converting spot colors into CMYK or Multicolor process colors. The ColorLogic solution offers printers the security of getting the best possible conversion of spot colors to process colors, in terms of colorimetry and printability.

Classic methods of spot conversion

To appreciate the special features of the new solution, we first need to take a look back in order to understand how the previous method for converting spot colors used to work in ZePrA and many other solutions: The Convert spot colors to target color space checkbox resolves spot colors (DeviceN colors without CMYK components) and converts them to the target profile. The substitute color (referred to as the alternate color space in the PDF) assigned to each spot color in the PDF file is used in this context and is processed using the color management settings in the Images/Vectors tab in ZePrA. The PDF alternate color value for a spot color is usually indicated in CMYK or Lab, and is specified in the graphic or layout application used to create the PDF (e.g. Adobe Illustrator, InDesign or QuarkXPress).

Given appropriate settings, ZePrA performs DeviceLink conversion from the alternate color space to the target color space. Nevertheless, conversion using the alternate color value is only an inaccurate solution, particularly if the alternate color for the spot color is indicated by device-dependent CMYK values. Even if the alternate color were to be indicated by a measured Lab value, ICC color conversion would usually result in converted colors that are not sufficiently accurate and, above all, not easily printable.

Example: The spot color PANTONE 266 C has an alternate color value of CMYK = 70/81/0/0 in a PDF document. When printed in a high-quality offset process on coated paper in accordance with ISO Coated V2, these CMYK process-color values would produce a dark violet color that is 29.2 Delta E-76 or 8.0 Delta E-2000 off the actual spot color (see screenshot). The color is outside the printable gamut and thus cannot be printed by 4-color offset printing.

On a Multicolor printing system with 7 process colors, which would be capable of wonderfully simulating the spot color, the same spot color with the same PDF alternate color value would likewise only be reproduced with a major color error of approx. 9 Delta E-2000.

Using this example, conversion via a stored CMYK alternate color value will result in highly unsatisfactory color reproduction in both printing processes.

Other types of approaches on the market

Lab alternate color values have been stored for spot colors in the PDF document since the launch of Adobe InDesign CS6. At first glance, Lab alternate color values appear to be a better alternative than CMYK alternate color values, but it creates other, sometimes even more serious problems when converting spot colors.

The screenshots (image) show how differently a spot color can be converted to CMYK with a Lab alternate color value. The spot color PANTONE Cool Gray 7C is highlighted in red in the original file in the screenshot on the left. The screenshot in the middle shows that conversion of this spot color by means of a standard tool leads to four process colors, which is highly unsuitable for printing. In contrast, the screenshot on the bottom right shows that conversion using ZePrA not only achieves the most accurate color reproduction, but also manages with the minimum number of channels (only the process color Black is used). Moreover, the screenshots (image)show that the spot color gradients converted with ZePrA have a far purer color appearance than the gradients converted using the standard tool.

Instead of alternate color values, other color server solutions on the market use a color library that contains the color values of the solid tones of the spot colors, measured in Lab. Rather than using the PDF alternate color value when converting spot colors to the target profile, these solutions take the Lab value of the solid tone from the color library and convert it to the target color space by the absolute colorimetric method. If the gamut of the target profile is large enough to be able to map the spot color, a good colorimetric match with the solid-tone value is obtained.

In our example using PANTONE 266 C, (image) this would be the case with our Multicolor printing process, and the spot color could be reproduced quite well with 1.9 Delta E-2000 (the screenshot on the right shows the color conversion that would be obtained with standard tools).

However, should the gamut of the target profile not be large enough and the spot color be out-of-gamut, only rarely would the best possible color value with the smallest Delta E be calculated, depending on the target profile used.

This is due to the inaccuracy of profiles and the Gamut Mapping used. The biggest drawback of simple colorimetric conversion is, however, that unwanted process color components can emerge (in our Multicolor process, for example, CMYK +Orange+Green+Violet = 3/3/6/0/5/0/87), impairing the quality of the printed image.

Just think of a text or a barcode that would thus be composed of several colors and be unsharp as a result of register problems when printed. At the same time, problems can arise when overprinting what were previously spot colors with process colors or other spot colors. Furthermore, a library that contains merely the measured solid tones permits only an incomplete prediction regarding the appearance of graduations of the spot colors. So, this approach is bound to fail and may, from the printing point of view, produce poorer results than converting the alternate color value by means of DeviceLink profiles, as previously done in ZePrA.

ZePrA’s Spot Color module features

Many users would like exact colorimetric conversion of spot colors. This results in a need for both, for color libraries with the correct, measured spectral color values and also for additional Delta E minimization. Delta E minimization would even make it possible to reproduce our specimen color PANTONE 266 C exactly and without a color error in the 7C Multicolor printing process (see screenshot below). (image)

Users would like to create and use several libraries, if necessary, for the same spot color because they need separate and optimized color values for different substrates and printing processes.

Similarly, the color libraries must work with measured graduations of the spot colors, so that the 50% value of a spot color, for example, can also be reproduced optimally.

To accurately calculate overprinting simulations, the measured values should additionally be stored in spectral form. Additionally, an intelligent, spectral color mixing model should be used.

It is also desirable if the color server is able to preserve overprinting properties to the greatest possible extent.

When dealing with elements consisting of a mixture of spot colors and other process colors, the color appearance should be simulated as accurately as possible following resolution of the spot color.

When converting to the target color space, the fewest possible process colors should be used, but the result should still yield the smallest possible visual color difference. In our example, the optimum solution is to use only the Violet process color (see screenshot below) and achieve a color error of just 0.8 Delta E-2000.

Some spot colors need to be converted to a specified target value (e.g. to a process color), regardless of the smallest possible Delta E. This is necessary for texts or barcodes, for example.

Similarly, some spot colors have to be excluded from conversion, e.g. cutting marks created as spot colors, varnishes or braille.

Application of Photoshop color corrections to PDF files

Colorimetrically generated DeviceLink profiles cannot be used in some applications. This is the case if, for example, a customer provides printing data and, instead of a correct proof, a print that needs to be matched as accurately as possible in production printing. If you open the printing data on a monitor with soft proofing based on the printing standard for production printing, there may be pronounced differences compared to the print provided by the customer.

Options for solving the problem: either to print outside the standard and try to adjust the specifications by using the gradation corrections in ZePrA, adjustments on the printing device or to apply Photoshop corrections to the PDF file.

Photoshop approach: has the advantage of applying standards to proof the color corrected data and have them approved by the customer. This method requires an person with Photoshop experience and CoPrA’s Edit module.(link)

The demo version of the programs allows a single test run with production data. The operator compiles color relevant objects, taken from the PDF data to be corrected in a file in Photoshop and combines the test data with the CoPrA Edit Chart. Then correct the test file on the monitor under soft proofing conditions. The edited image is loaded into CoPrA and the corrections are saved as a DeviceLink profile.

The DeviceLink profile can subsequently be used in ZePrA to correct the colors of the original PDF data. If necessary, these data can be approved by the customer on a proof before printing.

The printer can work according to a standard in the accustomed manner and reliably match the proof.

The individual steps for converting Photoshop corrections into DeviceLink profiles are described in the tutorial manual (link) for CoPrA.

ZePrA | Working with Transparencies

Working with Transparencies

Transparency Flattening and Sharpening

Many users often think of only photographic images when sharpening PDF data.  However, when flattening transparencies, vectors and texts can also be converted into pixel-based images. These pixel-based images are treated like photos when the Sharpening option is activated This can lead to adverse results. A difference in sharpness between adjacent objects in the form of a vector or text can cause visual issues and inconsistencies. For production, sharpening effects should always be tested in advance.

Use caution when flattening transparencies with ZePrA. Sharpening takes place before conversion and flattening. In contrast, sharpening without transparency reduction in ZePrA takes place after conversion.

Depending on the composition of the elements in the layout software on the one hand, and the parameters for flattening the transparencies and sharpening in ZePrA on the other, extreme sharpening can produce visually undesirable effects.

The negative effects only become apparent at the most extreme sharpening Amount with a Threshold of 0. Since JPEG artifacts usually show minimal color differences, a high Threshold is the most important factor to avoid unwanted effects.

The following example shows the effects of different sharpening levels. In this case, the graphic designer has placed an object with drop shadow over a gradient.

When flattening the transparencies, the flattened elements were compressed using the JPEG format. With an extreme sharpening setting, the artifacts part of the gradient underneath the drop shadow, which is usually invisible, become intensified when converted into a JPEG image. The following sharpness settings were used from top to bottom:

  • No Sharpening
  • Radius 0.35 points, Amount 80, Threshold 8
  • Radius 0.35 points, Amount 300, Threshold 4
  • Radius 0.35 points, Amount 500, Threshold 0

 

Converting PDF files containing transparencies

When converting PDF files with transparencies, the transparencies can either be preserved or flattened using Transparency Flattening.

During conversion, each object – with or without transparency – is converted separately, preserving the structure of the PDF document.

Unfortunately, there are so many variations in the blending of transparencies and the stacking order of semi transparent objects that there is no simple rule as to when transparencies ought to be flattened or not.

Flattening requires the resolution of the platesetter to be specified; therefore, it is best to perform transparency reduction as late as possible in the workflow.

ColorLogic recommends performing the conversion in ZePrA first without transparency flattening and then to check the converted file with a transparency-compatible PDF viewer (e.g. Adobe Acrobat Pro or Callas PDF Toolbox). If the converted file is visually correct and the desired total amount of coverage is maintained, continue working with the file.

If the file contains artifacts after conversion, uncheck the Convert all transparent Elements in PDF Files checkbox under Configurations/PDF and convert the file again.

This changing this setting often helps to preserve the impression of the original file (see figure below), since ZePrA excludes certain transparency modes from the conversion.

The checkbox Convert all transparent Elements in PDF Files is active by default.

However, if there are still artifacts after deactivating this function, use Transparency Flattening.

Note: Transparency Flattening is based on the Callas SDK, which in turn uses Adobe’s PDF engine for transparency flattening. Therefore, the results achieved with ZePrA’s Transparency Flattening are identical to those achieved with the current versions of Callas pdfToolbox.

Converting Spot Colors containing Transparencies

For transparency flattening of PDF files containing transparent objects composed of process and spot colors, Adobe’s transparency flattening preserves spot colors to preserve the impression of the original but sets them to “Overprint”. Transparency-reduced PDF files should therefore always be viewed with “Overprint preview” enabled in the PDF viewer (e.g. Adobe Acrobat Pro). Simple PDF viewers, such as the Preview in macOS, or many apps on tablets, display such files incorrectly due to the missing overprint feature.

If ZePrA is to be used for high-quality spot color conversions instead of the PDF preflight program or the RIP, activate the checkbox Convert Spot Colors under Configurations/Spot Colors and spot colors are converted to process colors in the best possible way.

Note: Spot colors that are converted will be set to “Overprint” due to the transparency reduction and can mix with process colors. This can lead to unwanted results and the disappearance of converted spot color objects. If this happens, select Transparency Flattening and either Dissolve Overprinting or use the extreme method Rasterize Document.

Transparency Flattening, Image Quality, and File Size

When reducing transparencies, the resulting rasterized objects are created with lossless ZIP compression. This guarantees the best quality but also results in larger files compared to JPEG compression. Even PDF files with JPEG-compressed images will have ZIP-compressed images due to transparency flattening. If the file size is to be reduced, and a reduced quality is acceptable, change the Compression Method to JPEG (in the Image Quality panel under Configurations/Options).

Note: The Compression Method is only considered by ZePrA when performing a conversion. When performing a Transparency Flattening without conversion, no compression change is made, and rasterized objects are ZIP-compressed.

Sharpening for in-house RGB workflows

Sharpening

(For example, in-house RGB workflows)

Sharpening Images

Optimal sharpening refers to the scaled final format of an image in the print data. The following section assumes that editing high-resolution RGB images, placing these images in the layout program, creating the PDF data, and processing the data with ZePrA are connected workflows within an application suite. The summary of these steps is referred to here as an in-house RGB workflow.

With in-house RGB workflows it is possible to work with high-resolution originals of the RGB images in the layout program and then generate a PDF/X-3 or PDF/X-4 file that also contains high-resolution RGB images. Finally, ZePrA handles the color management, the downsampling to the final resolution, and the sharpening. 

After the RGB images have been reduced to the final resolution and color converted to CMYK, a stronger sharpening than is usual for pre-sharpened CMYK images should be applied in ZePrA. To do so, select Strong Sharpening of RGB and Gray Images in ZePrA under Configurations/Options/Sharpening/Preset.

For documents that contain RGB images and already sharpened CMYK images it is recommended to limit sharpening in ZePrA to RGB images.

Note: If transparencies are used in the layout program, it is essential to ensure that there is no  transparency reduction, as RGB data is inevitably converted to CMYK if the RGB image is affected by transparent objects. Transparency reduction is mandatory when creating PDF/X-3 files, whereas transparency is explicitly allowed in PDF/X-4 files. If all RGB images are sharpened in ZePrA, the transparency reduction, should also take place in ZePrA.

Softproofing and PDF images

Softproofing PDF image files

Softproofing in ZePrA offers a true color presentation of jobs on the monitor, with overprinting elements and transparency effects also displayed correctly.

Creating a softproof:

  1. Go to the Navigation Panel and open Overview/Jobs and Queues Overview.
  2. Right-click on a job in Pending Jobs or Processed Jobs to open the context menu.
  3. Select the option Screen Preview. The file is displayed in a window.

Activate the Softproof Color Management Settings via the colored icon in the title bar of the window.

Simulation Profile: The colors will be rendered through the selected Simulation Profile to the monitor profile. As a default, the output intent that ZePrA has embedded in the processed file will be used and shown in brackets. The setting is similar to the Output Preview in Adobe Acrobat

Note: The Default Profiles on top of the dialog and the Prefer embedded Profiles checkbox are only relevant in the case that the simulation profile differs from the color spaces in the file itself.

Rendering Intent: A color conversion method (rendering intent) must be selected for calculation. Typically, only rendering intent directly from the Simulation Profile chooser needs to be selected. The rendering intents include not only the normal ICC intents and relative + Black Compensation, but also include three special ColorLogic intents:

Relative+ and Absolute+: have an impact if the black point information contained in a relative matrix monitor profile indicates that the black point is lighter than L* = 0. The softproof becomes a little darker as a result of this, which usually leads to a visually better match with a reference proof.

Relative Lightness: Based on the absolute colorimetric intent with paper color simulation. The lightness of the paper color simulation is scaled to the maximum displayable lightness of the monitor, the color of the paper color simulation and the gray balance of the softproof as a whole being preserved. This setting makes sense if the absolute colorimetric softproof is visually too dark, as is often the case in newspaper printing for example.

If there is no Simulation Profile available in the file (no profile shown in the brackets), select the desired profile from the drop down list. For rendering intent, we recommend relative or absolute colorimetric or ColorLogic rendering intents.

For monitor presentation, the monitor profile stored in system is automatically selected.

Click Apply to visually display the settings and Save to save the window with the settings and then close it. Next time the window is opened the settings will be retained.

Note: In order to select the correct softproof intent, it is generally advisable to use not only the monitor, but also a dimmable standardized light box with a reference proof for visual comparison.