Transparency/ Overprinting

Flattenting Options for High Quality Conversions

Flatten Transparencies

If the file contains transparencies that require flattening, ColorLogic recommends using the Transparency Flattening option in the PDF tab.

Transparency Flattening Methods:  Choose between two options – either Flattening or Rasterizing the entire file.


Presets will cover most of the day-to-day tasks for transparency reduction. The Presets can also be the basis of a Custom setting, e.g. for the resolution of the platesetter. The detailed options for Transparency Reduction are similar to those used in the Callas PdfToolbox and Acrobat Pro.

Transparency Reduction presets:

High Resolution for Printing: Use this preset for print production, for example with a conventional printing press. The most possible vector objects are preserved. In screening, a typical imagesetter resolution of 2,400 dpi is used for vectors and texts. The preset High Resolution for Printing is the default setting when enabling Transparency Reduction in ZePrA.

Dissolve Overprinting: Use this option if there are issues with overprinting elements after color conversion or the total area coverage (TAC) is too high. This preset is usually the best solution to eliminate overprinting issues, especially combinations of spot color conversion and transparency flattening. The elements are dissolved into individual vector objects and, if necessary, rasterized so that the resulting color impression is identical to the original file. The major difference between High Resolution for Printing and Dissolve Overprinting is the Preserve Overprints checkbox is disabled.

Note: The two options Preserve Overprints and Preserve Overprint Appearance are independent from each other. If the checkbox Preserve Overprints is disabled, all overprinting objects will be flattened the same way as transparent objects. In both cases (overprinting objects and/or transparency flattening), if spot colors are involved, a downstream spot color conversion may lead to unwanted results. Use Preserve Overprint Appearance to avoid the issue.

Rasterize all Graphics and Text: When the Pixel/Vector Balance is set to zero, all vectors and text are rasterized. The resolution of the rasterized elements then corresponds to the Vector and Text Resolution.

Tip: Images are also converted to this resolution and may be enlarged in resolution and more blurred in print. The resulting PDF files may be much larger through application of this preset.

Resolution for Proof Printing: Overprinting elements are dissolved in order to correctly render the color appearance of overprinting elements.

Custom: The options become available to set custom options for resolution and overprinting:

Pixel/Vector balance: Determines the amount of vector information to be preserved. A higher setting means more vector objects are preserved and a lower setting means more vector objects are rasterized. Intermediate settings preserve simple regions in vector format and rasterize complex areas. Select the lowest setting to rasterize all graphics with transparency.

Note: The conversion to pixel images performed depends on the complexity of the page and the types of overlapping objects.

Resolution for vector and text: All objects with the specified resolution are rasterized, including images, vector graphics, text and gradients. The resolution affects the accuracy of the intersections during conversion to pixel images. According to Adobe, the resolution of vector graphics and text should be set somewhere between 600 and 1,200 ppi in order to achieve high quality screening, especially with serif fonts and small fonts.

Gradient and mesh resolution: Specify a resolution of between 72 and 2,400 ppi for gradients and illustrator grid objects that were rasterized as a result of reduction. The resolution affects the accuracy of the intersections during conversion to pixel images. According to Adobe, the resolution for gradients and grid objects should be set somewhere between 150 and 300 ppi because the quality of gradients, drop shadows and soft edges does not improve with higher resolutions. Higher resolutions can increase printing time and increase the file size unnecessarily.

Convert text to outlines: Converts all text objects to outlines and ignores all type glyph information on pages with transparency. This option ensures that the width of text remains unchanged during reduction.

Note: Small fonts appear slightly wider if the file is opened in Acrobat or printed on printers with low resolution. The quality of the text is not affected when outputting to printers with high resolution or platesetters.

Convert strokes to outlines: Converts all strokes on pages with transparency to simple filled outlines. This option ensures that the width of strokes remains unchanged during reduction. Please note, thin strokes appear slightly thicker and reduces conversion performance.

Clip complex regions: Ensure boundaries between vector and rasterized graphics fall along object paths. This option prevents visible transitions with graphics when one part of an object is converted to a pixel image while another part of the object remains in vector form. However, selecting this option may result in paths that are too complex for the printer to handle.

Preserve overprint appearance: Solves general overprinting issues without rasterizing the file. This technology may be used when of overprinting issues with or without transparencies in the file. Since ZePrA 4.5 this technology has been activated by default in all Presets within our Transparency flattening feature. Especially during conversion of spot colors to process colors, the preset Dissolve overprinting should be used to ensure the best possible conversion of colors and vector objects.

Use the document colors space as transparency color space on page level: Overwrite the transparency blending space on page level and will use the profile defined as Document Color Space in the respective configuration. Useful when a file with RGB transparency blending space is converted from CMYK to CMYK. In this case, a more reliable result will be achieved if the transparency blending space is CMYK and not RGB. This option can be enabled with a Custom Preset.

Rasterize Document: Completely rasters the PDF file using the Resolution specified. Vectors, text, images and the white paper background will be included. This setting can be useful when printing to an older RIP that does not support transparencies or generating a soft proof as an pixel based file. Under Format select either a PDF or converted to a Pixel file.

Note: If Pixel file is selected, specify in the Options tab > Image quality for the TIFF, PSD or JPEG file. Using the Automatic mode for the Compression method as image quality typically a TIFF file will be generated. Please note that for multipage PDF files will be created for as many pages the document has.

Smooth text and vector graphics: Anti-aliasing is performed on text and vector elements avoiding artifacts when a low Resolution is selected. Anti-aliasing may also cause a slight blur in the processed file.

Note: The font(s) are also rasterized with this option. For the best results, select a high enough resolution (minimum 600 dpi) in order for rasterized text and vector lines for a quality result.

Read more about handling transparency flattening