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

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.

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.

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.

Extra spot colors may be required or unnecessary depending on the print job. The preflight allows you to determine whether the number and labeling of the color channels are appropriate for the print job.

Undefined spot colors can be processed using ZePrA’s spot color module. If the spot color module has not been licensed, spot colors can at least be converted using the alternate color space (PDF). This provides the same results as a preflight program. Further information on the spot color module can be found in the Spot Color Processing chapter.

Once the job has been processed in ZePrA, the spot colors occurring in the PDF file can be checked by right-clicking on the processed job in the Overview to open the context menu and selecting Show Job Properties to open the Job Report. This is particularly useful when not using an additional preflight program.

For fully automated workflows that are running without additional approval by the customer, we recommend printers only accept pure CMYK PDF files that have correctly embedded profiles. For other data, we recommend to optimize them with ZePrA and then send a low-res CMYK soft proof to the customer for approval.

Note: A standard queue created with Auto Setup (Normalize and convert Colors to new Output Condition) that uses the SmartLink function optimizes all RGB, CMYK, and Gray objects of a PDF file by using DeviceLink profiles. Any embedded profiles are taken into account in the conversion. Alternatively, a standard queue can be duplicated to change the handling of embedded profiles (see next section Ignoring CMYK Objects with Embedded Profiles).

The profiles embedded in the PDF file can be checked after job processing by right-clicking on the processed job in the Overview to open the context menu and selecting Show Job Properties to open the Job Report.

In some workflows, especially in print shops, it is common to remove embedded profiles from CMYK objects (images and vectors). It is often assumed that the profiles have been added incorrectly and will cause problems in a subsequent ICC conversion.

When the SmartLink function is not licensed, this procedure follows the default setting for Auto Setup queues. When the SmartLink function is licensed, embedded profiles are taken into account. SmartLink conversions, which preserve primary and secondary colors, as well as separation, ensure clean conversions.

If embedded profiles are to be ignored or the SmartLink function is not to be used - for example, in Auto Setup queues for normalizing and color conversion or for SaveInk applications - deactivate the corresponding checkboxes (Apply Embedded Profiles/Intents or Apply SmartLink) in the Images/Vectors tab. This ensures that embedded CMYK profiles are not used. Instead, select Same as Document Color Space and convert with the profiles set in the Document/Target tab.

For print shops, it is important that the specifications for the data delivery and the order confirmation clearly indicate the maximum Total Area Coverage that is expected for the type of paper to be used and also the printing standard the client should prepare the printing data.

When printing on newspaper or uncoated paper and the maximum Total Area Coverage is significantly exceeded, this indicates that image data has not been optimized for the respective printing standard. Usually these are image data for coated paper in offset printing.

When optimizing PDF files via standard queues in ZePrA, the following alternatives are available in Auto Setup:

Normalize and convert Colors to the new Output Condition: Converts the data - for example from coated paper to uncoated newspaper paper - and optimizes the color appearance.

Optimize Total Area Coverage (TAC): Limits the maximum total amount of color without changing the color appearance.

Checking overprinting CMY objects without any black is a rather rare special case. Regarding high color stability during production, fast drying times, and ink savings, we recommend using ColorLogic's SaveInk queues for as many print jobs as possible.

However, if an overprinting object of a PDF file is composed of all CMY colors without any black, the resulting color impression from the overprinting object and the background may change after color optimization, due to the overprinting rules of the PDF standard. For an underlying object, the color of a channel is only completely visible if no color is present in the respective channel of the overprinting object. If an overprint object has just a slight amount of color in a channel, then only the color component of the upper (overprinting) object is visible.

If CMY parts of SaveInk profiles are unintentionally replaced by black and the overprinting behavior changes as a result, but the color is still to be saved, a new SaveInk profile must be created for which the exception Preserve 0% Black is activated. This special exception is located in the SaveInk module of the CoPrA profiling software.