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 it’s Update Profile module is integrated in the SmartLink module 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 colors as before, just a few details are required, such as the spectral measurements of dot gain strips or the Ugra/Fogra Media Wedge or, better still, the Reprofiler measuring strips that we provide with CoPrA.

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

Make sure you use a control strip in your printing process that can be read by the Update Profile of CoPrA.

Two types of Reprofiler control strips for different measuring instruments (X-Rite i1Pro and single-patch measuring instruments) are included in the scope of delivery for both CMYK and RGB-based printing systems.

The CoPrA’s own color control strips should preferably be used for creating optimized profiles. The CoPrA Reprofiler control strips include the 100% values in the shadows and for overpinting patches that are important for profile creation.

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.

We recommend that the ColorLogic control strips always be used when optimizing digital printing systems since only they can ensure accurate determination limitation of the black point of the printing system.

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. The measurement file must not contain more than 150 patches.

Once you have printed a control strip of your choice, you then measure it using a spectrophotometer.

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.

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:

  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 Profile dialog.
  3. 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.

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 in brackets.

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

Flattened transparencies and sharpening

Many users tend to think only of photographic images when it comes to sharpening in PDF data. Through flattened transparencies, vectors and text can result in pixel images. These pixel images are treated exactly the same as photos if sharpening is active in ZePrA. This may lead to unwanted artifacts. Differentials in sharpening between neighboring objects (which could be preserved vectors or text), can cause visual dissimilarity. Test the effects prior to production.

When flattening verify the transparencies in ZePrA verify the results. In this case, sharpening is performed prior to color conversion and flattening. Without transparency flattening, ZePrA would apply the sharpening after color conversion.

Depending on what the interplay of elements in the layout program, the parameters for flattening the transparencies and the sharpening parameters in ZePrA look like, extreme sharpening can lead to undesirable visual effects.

transparency-sharpness

The negative effects are revealed only with the most extreme sharpening strength and a threshold of 0. Since JPEG artifacts usually exhibit only very small color differences, a high threshold is the most important criterion for avoiding undesirable effects.

The following example demonstrates the interaction with various levels of sharpness. In this (image)case, the graphic artist has placed an object with shadows over a gradient. In flattening the transparencies, the flattened objects were compressed in the JPEG format. With extreme sharpening, artifacts which are not normally visible are intensified in the part of the gradient that has been changed into a JPEG image through the overlying shadows. From top to bottom, the following sharpness settings were applied:

No sharpening

0.35 points, Amount 80, Threshold 8

0.35 points, Amount 300, Threshold 4

0.35 points, Amount 500, Threshold 0

Converting PDF files with transparencies

ZePrA can be used for the color management of PDF files with transparencies. Choose to preserve transparencies or flatten them via Transparency flattening. The ZePrA approach for color conversion, when preserving transparencies, is that every object – with or without a transparency – are color converted individually, the structure of the PDF document being preserved. There are many variations for the blending of transparencies and the stacking order of semi-transparent objects that there are no rules defined regarding when transparencies should be flattened to avoid unwanted color shifts when converting the colors.

Flattening requires resolution to be specified for platesetters. Whenever possible, avoid flattening until later in the workflow. ColorLogic recommends first converting the colors without flattening the transparencies in ZePrA and examine the results in a transparency compatible PDF viewer (e. g. the latest version of Adobe Acrobat Pro). If artifacts are evident in the file following color conversion, try deactivating the Convert all transparent elements in PDF files checkbox under Configuration/PDF and convert the file again.

flattenting-issues

In many cases, deactivating this option helps to preserve the impression of the original file (see also the example in the middle) (image) because ZePrA excludes certain transparency modes from color conversion. The option should, however, be activated as standard.
If deactivating the Convert all transparent elements in PDF files option does not eliminate artifacts, the next step is to enable Transparency flattening in ZePrA (in the PDF tab).

Note: Transparency flattening is based on the Callas SDK, which in turn uses the Adobe PDF Engine for transparency flattening. The results from ZePrA are the same with current versions of Acrobat Professional and Callas pdfToolbox.

SaveInk and TAC reduction for PDF files with transparencies

Auto Setup queues do not activate transparency flattening as standard with Save Inks or Optimize TAC. In many cases, transparency flattening is not necessary, especially for PDF files with normal transparencies such as drop shadows. However, there are certain situations where transparency effects change the color appearance, despite high quality SaveInk profiles, or where the total area coverage is exceeded despite correct reduction profiles. ColorLogic recommends that following TAC reduction and SaveInk application; examine the total area coverage using a modern preflighting program that takes into account transparencies. If, for performance reasons, you cannot, or do not want to, examine every file, then we recommend that you activate Transparency flattening in the configuration.

Converting spot colors with transparencies

When PDF files, that include process and spot colors, are flattened, the Adobe transparency flattening provides that spot colors are maintained. However, in order to preserve the appearance of the original file, they are set to overprint. Overprint preview should always be enabled when viewing flattened PDF file in the PDF viewer (e.g. Adobe Acrobat Pro). Basic PDF viewers, such as Mac Preview and many apps on tablets, lack overprinting support and display these files incorrectly.

Should ZePrA be used for high-quality conversion of spot colors to the output profile instead of the PDF preflighting program or the RIP, optimally convert spot colors into process colors under Configuration/Convert spot colors. Please note, that due to transparency flattening, converted spot colors may be on overprint and mixed with process colors. This can lead to unwanted results and the “disappearance” of converted spot color objects. If this occurs, use the transparency flattener preset Dissolve overprinting. The most extreme method to would be to rasterize the file completely.

Transparency flattening, image quality and file size

With transparency flattening, ZePrA creates the resulting rasterized objects with lossless ZIP compression. This produces the best results in terms of quality, but also results in a larger file size compared to JPEG compression. Even in the case of PDF files with JPEG-compressed images, transparency flattening results in ZIP-compressed images. If you want to reduce the file size and can accept a drop in quality, then you can switch the configuration of the Compression method to JPEG in the Image quality section of the Options tab.

options-main-1

Note: ZePrA only takes the compression method into account when performing a color conversion. If performing transparency reduction without color conversion, in ZePrA then no compression modification is made and rasterized objects will be ZIP compressed.  

Sharpening for in-house RGB workflows

Sharpening

(e.g. for in-house RGB workflows)

Sharpening Images

Optimal sharpening refers to the scaled end format of an image contained in the printing data. In the following section, it is assumed that the processing of high resolution RGB images, their placement in the layout program, the creation of PDF data and the application of ZePrA is a continuous workflow within the same company.

In-house RGB workflows provide the option to work with high-resolution originals RGB images in the layout program and then create a PDF/X-3 or PDF/X-4 file that also contains the high-resolution RGB images. Color management, downsampling to the final resolution and sharpening for the PDF file are performed in ZePrA. After downsampling of RGB images to the final resolution and color conversion to CMYK, use stronger sharpening in ZePrA than normally used on pre-sharpened CMYK images.

Procedure: Select Define Configurations/Sharpening/Preset strong sharpening of RGB and Gray images. For documents that contain mixed image data set of RGB images and presharpened CMYK images, you should restrict the sharpening in ZePrA to RGB images.

strong-rgb-sharp

Note: To sharpen all RGB images in ZePrA, do not perform any transparency reduction in the layout program, for optimum results sharpen the images in ZePrA.

Enabling transparency reduction in the layout software results in converting RGB data to CMYK if the RGB image in the layout program is adjacent to transparent objects. During generation of PDF/X-3 files, transparency reduction is mandatory, while in PDF/X-4 files, transparencies are explicitly allowed.

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.

Use of Multicolor profiles

Use of Multicolor profiles

Use of Multicolor profiles

ZePrA works with Multicolor printer profiles or with DeviceLink profiles that permit RGB-to-Multicolor, CMYK-to-Multicolor or Multicolor-to-Multicolor conversion.

Using Multicolor profiles in a PDF workflow

ZePrA features the option of using Multicolor profiles both as the document color space and target profile and using Multicolor DeviceLink profiles for color conversion.

Particularly in prepress work for packaging, this is an important option when image data are present in the form of an RGB or CMYK file. First, you can place RGB and CMYK image files directly in the finished document. From this, you create a PDF file and convert the complete document in ZePrA to the required Multicolor color composition for printing. Another interesting field of application is the printing of photo books by so-called HiFi color printing processes using 6 or 7 inks.

Note: An Multicolor module is license required (available in the XXL package) to utilize Multicolor functions.

When preparing the data in ZePrA, the result is known as a DeviceN PDF file, where every channel is named the same as channel name of the Multicolor target profile. DeviceN is the standard color definition in PDF for describing spot colors for print production. It offers a high degree of compatibility with the proven spot color processing functions of common application programs. The PDF files generated can usually be assessed in the Output Preview of the current version of Adobe Acrobat Professional and processed with current PDF workflow systems. Positioning of the PDF files in, and export from, current Adobe InDesign documents also present no challenges. ZePrA supports the PDF/X-5n standard, which enables the embedding of Multicolor profiles in PDF files.

When configuration is created with the Auto Setup wizard (selection of a Multicolor DeviceLink profile), the default setting is such that the Multicolor target profile is not embedded in image data, but that it is embedded as the output intent in PDF files. When a converted PDF/X file (e.g. a PDF/X-4, X-3 or X-1a file), the color converted file is changed into a PDF/X5n file.

Before using your Multicolor printer profile, which was selected under Define Configuration as the Target Color Space in the Target tab, or in the Document Color Space tab when it is  a Multicolor DeviceLink profile, verify whether the channel names and Lab color definitions have been entered in accordance with your specifications.

If the Embed into output file checkbox is activated, ZePrA uses the channel names and color definitions from the Multicolor printer profile set as the target color space when creating the color converted PDF file.

When Embed in output file is not checked, the channel names and color definitions are adopted from the Multicolor DeviceLink profile. Verify that the identical channel names and Lab color definitions in the target profile and the DeviceLink profile. With the help of the CoPrA’s Profile Manager, rename the Colorants (description of color channels) in accordance with your specifications and also enter the Lab color definitions in every Multicolor printer profile and DeviceLink profile.

Depending on the Multicolor profile used, the channel designations contained and the subsequent workflow outside ZePrA, we recommend that you test the complete workflow beforehand to make sure that everything runs smoothly.

Converting image data with Multicolor profiles

For converting image data with Multicolor profiles, ZePrA supports PSB, PSD, TIFF and JPEG files. Since the current file format specifications (as at May 2014) do not provide for embedding Multicolor profiles in TIFF, JPEG, PSB and PSD files, for image data conversion ColorLogic recommends deactivating Profile Embedding in the Document/Target tab. We recommend that image data to be converted to Multicolor should be saved as PSB/PSD files from Photoshop and then processed using ZePrA. Adobe InDesign can be used to process any PSB/PSD image files converted with ZePrA by means of a Multicolor target profile.

When converting the image data of Multicolor files, ZePrA distinguishes the following cases, which can be set in Configurations under Options/Image quality:

If the channel designations of the Multicolor target profile are CMYK+X, a TIFF file is created providing Preferred lossless format is set to TIFF.

If the channel designations of the Multicolor target profile are not CMYK, then a PSD file is created.

Note: TIFF only supports CMYK+X.

If the compression method is set to Automatic, the ZePrA will try to preserve the format or create a TIFF file. However in the case of a JPEG file or a non-CMYK Multicolor file, a PSD file is created.

Note: JPEG does not support Multicolor color spaces.