Optimized workflow in digital printing – Part 2

Science & Technology

Support-independent production

Optimized workflow in digital printing – Part 2 Producers of support-independent printing data can save a lot in terms of work and data. The point at which data needed for the final colorimetric space is converted remains totally under the control of the data creator. The only important thing is that the conversion occurs as late as possible. How to proceed?

Digital printing data can be created on the basis of various givens.

On the one hand there is data processed expressly for digital printing; on the other, you can create data for offset printing and then reproduce it in digital for other purposes.

At this point, printing-service suppliers have to differentiate, in digital printing, the way in which data will be finally processed. In general there is a choice between two procedures.

• Data optimized for offset printing: Because of the difference, from the color standpoint, between offset and digital printing (in depth work you can get much better results in offset than in digital, while in color variety and brightness digital printing surpasses offset in many fields) in most cases it’s impossible to get truly 1:1 reproduction because print supports generally have limitations in regard to depth and chromatic range. The aim must be to optimize output in order to produce an image as similar as possible to the one desired.

• Data optimized for digital printing To take full advantage of the possibilities the color range offers in digital printing, you cannot limit it in the preliminary stage while creating printing data. All too often you hear the question “How should I deliver the data” and the reply: “Create data for ISP Coated v2 and deliver it in PDF/X-1a or PDF/X-3”. The only correct reply should be “Create the data independently from the support in RGB (equipped with profile of course) and generate a support-independent PDF/X-4 document”.

The difference between ISO Coated v2 and printing material in digital printing.

process - Durst news for screen and digital printers - Issue 69 - February 2011

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The goal determines the route.

Preparatory work

So in digital printing do you always have to have the goal clearly in mind? Do you want to get the best from digital printing where color quality and variety are concerned? Or simply reproduce the best 1:1 result possible?

One thing should be clear. If, for example, an image is already trimmed in the colorimetric space (color information having already been lost) you can optimize the image (i.e., improve color variety) only by analyzing the image and automatisms, whose results are only as good as the technology behind them, and the base image - information that can be gotten mostly from the image. However, predictability does not exist because this may work with one image and not another.

Both routes have to be considered separately. In this second part of our analysis I would like to describe the ideal case: creating from InDesign CS5 a support-independent PDF/X-4 file as an output base in digital printing, suitable for any printing material. Although many people believe that the “ideal case” doesn’t exist, what they should do is try to “live” the ideal case and not continually limit possibilities.

Prior to digital production you need to complete some preparatory stages. You need to: • Install updated versions of software: Has an updated version of the software been installed? Here I start from InDesign CS 5 7.03, Illustrator CS 5 15.02, Photoshop CS 5 12.02 and Acrobat Professional 9.4.1 or Acrobat X Professional.

Download the latest versions from the Adobe website and install the updates. This will prevent surprises in PDF creation.

• Get current color profiles Here you have to distinguish between two situations: 1. Print support ICC profiles: for your own production, install the current ICC profiles for the printing materials used. These are utilized only for the Proof Simulation of data on the screen. However, up to this point these profiles are not strictly necessary in producing supportindependent printing data.

2. Standard profiles for offset printing: they are included in the standard installation of every layout and graphics station because, when possible, support-independent data are created in the eciRGB v2 colorimetric space.

Load current eci_offset_2009.zip or ecirgbv20.zip profiles in http:// www.eci.org/doku.php?id =de:downloads.

• Install the profiles Decompress the ZIP files and copy (only) the profiles into the system directory – Mac OS X: Hard Disc/Library/ColorSync/Profiles or Windows: C:\Windows\System32\spool\driver.

• Define color-management configuration in Photoshop: Even if we are producing independently from the support, it’s absolutely necessary to have a color-management configuration. This is because we want to give the support-independent data the right profiles and on the screen evaluate output simulation. Start with file creation for Adobe Photoshop CS5 color configuration and open the dialog box to configure colors with the Bearbeiten • Farbeinstellungen (Process – Color configuration) command. If you have an output profile for the printing material you can save the color configuration setting. Saving the color-configuration setting for a printing material makes sense only if you have to create files primarily for a given material.

Nevertheless, for offset printing, at least for paper classes 1 and 2, you should create a color-configuration setting. Enter the values in the dialog box on the basis of the image and save this configuration in ISOCoated_v2. This setting will be used to synchronize the colors in Creative Suite.

process - Durst news for screen and digital printers - Issue 69 - February 2011

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Science & Technology

The values entered to configure the colors for a given printing material have to be handled like configurations for class 1 paper. Instead of ISOCoated_v2, select the ICC profile for the print support.

• Adapt the color-management configuration to InDesign: In order for the structure of a support-independent layout, at times containing other chromatic definitions (which we do not want in the ideal case) to work, you have to further modify the standard configurations, which have been completed through synchronization.

Start up InDesign CS5, select configuration from the dialog box with the Bearbeiten • Farbeinstellungen (Process – Color configuration) command and modify the CMYK value in the Farbmanagement-Richtlinien (Color-management directives) saved in the incorporated profile.

Save the modified setting under another name.

To tag it as a configuration for InDesign, you can simply precede the name with the letters ID.

• Synchronize the color-management configuration: This configuration must be exported into all Creative Suite programs.

Use Adobe Bridge CS5. Boot the program and select Bearbeiten • Creative Farbeinstellungen (Process – Creative color configurations).

From the color-configuration list on the screen select the alreadysaved setting and click on Anwenden (Use). The dialog box will close. To check, reopen the dialog box, which should be similar to what follows.

Using the selected settings the assigned profiles aren’t easily eliminated from CMYK data and the user is led to believe that his/her CMYK images are found in the same colorimetric space. So a CMYK to CMYK compensation may occur.

Even though, as described below, all the images are saved in RGB, this modification belongs to standard procedure, because often, unfortunately, we are not just dealing with the “ideal case”.

Preparation is ended, and the following tips can be correctly put to use.

Now it’s time to create a support-independent file.

And here I want to deal separately with recommended procedures for pixel fields, vector data and layouts.

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Processing pixel images For support-independent production, all pixel images have to be processed, optimized and saved in RGB. Image data is opened in Photoshop, processed from the color standpoint, retouched and finally saved with the assigned ICC profile. The ideal “save as” formats are TIFF, PSD or JPEG. However, depending on the departure situation, different steps are required before being able to save the image.

Before processing the image, and depending on the situation, image data should be treated as follows.

• The image is RGB and has an origin profile: At this point we have to start from the supposition that the origin profile of the RGB image has been saved, not by error but in a suitable way by the application that produced it, and that it is correct.

The data have to be processed in their output colorimetric space and saved with this profile. And if, when opening the file, a dialog box for colors appears, select Eingebettetes Profil verwenden (anstelle des Arbeitsfarbraum) (Use incorporated profile) (instead of work colorimetric space).

• The image is RGB without an origin profile: This data should open with the same option.

From the color standpoint, these images may differ considerably from the original. So you should check whether another origin profile could guarantee chromatic neutrality better. Give the image another origin profile with the command Bearbeiten • Profil zuweisen (Process – Assign profile) and select one of the four profiles available.

The profile used will depend on the observer’s visual judgment. Choose the suitable profile from AdobeRGB, sRGB, AppleRGB or ProPhoto.

Assign the profile you think is suitable and never again save an image without an origin profile! A calibrated monitor and a bit of sensitivity to colors are undoubtedly other important factors in not leaving judging capacity to mere chance.

• The image is CMYK without an origin profile: Because when opened the image is assigned the currently set CMYK profile as standard, you will see the image in the colorimetric space that is currently set. If in work preparation you have chosen the color configurations for the print support, you will see the result in output.

If, instead, ISOCoated_v2 was selected, you will see the result gotten in offset printing on class 1 paper. Since for the structure of support-independent data we want RGB data, here too you have to first produce a result satisfactory from the color standpoint by assigning and afterwards converting the image in an RGB work colorimetric space.

Upshot: the images not assigned an ICC profile make everyone’s daily work harder!

So that during image processing you can also see what is expected from the printed result, select Ansicht • Proof einrichten • Benutzerdefiniert (Image – Set proof – User-defined) and choose the destination colorimetric space (printing material) in the dialog box visualized as an ICC profile. Activate proof simulation with (cmd) + (Y) or (Strg) + (Y).

Thanks to the larger chromatic range, in image processing you should no longer have to touch certain chromatic spaces, or, if the ISOCoated_2 simulation has been activated, the paler spaces should be “saturated”.

Print-support simulation

ISOCoated_v2 simulation

• The image is CMYK and has an origin profile: Convert the CMYK image to RGB. The simplest thing is to convert the image in the eciRGB_v2 colorimetric space set in the work colorimetric space. Converting does not lead to color variations.

Save the image, always with the assigned ICC profile. Choosing another RGB-origin colorimetric space is possible and correct (unless the image isn’t converted in the profile used by the monitor).

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Processing vector data

Creating the file layout.

In the case of vector data, a distinction has to be made.

Were default color-management settings previously modified in InDesign? You can create a new document and start with the layout.

Now InDesign contains the original chromatic space of all the positioned files.

However, if a document was created earlier, what regarded color management is probably incorrect. In this case, when the InDesign document is opened a color warning pops up.

• Logos: Normally, for all types of logo output the numerical values of the colors must absolutely be maintained. No responsible person would accept cyan values “mixed” into an originally pure yellow space.

Don’t create this vector data independently from the support! As we described in part 1 of this analysis, the disadvantages deriving from possible reproduction errors can be greater than the advantages. In this case, make sure that the surfaces, gradations or black outlines of these objects are created correctly as 4c-Schwarz (4c-Black).

For digital printing the special case of “Black” must be dealt with separately.

• Illustrations: Create them independently from the support as an RGB vector graphic.

Here, too, use the RGM work colorimetric space set as eciRGB_v2.

Even in programs for vector graphics, such as Illustrator and CorelDRAW, color simulation for the selected print support can be visualized on the screen.

So adapt color configurations to the document and in each case select Alle Profile aktivieren (Activate all profiles) in the Platzierter Inhalt (Positioned content) menu. This re-establishes parity with the predefined setting, with which it’s once again possible to produce independently from the support.

How should you create colored surfaces in InDesign? With the same procedure used for vector graphics. If you are dealing with chromatic values, which in digital printing have to be maintained, the surfaces must not be created as support-independent. If the colors in the InDesign document have to be as close as possible to the colors of the printing material, then the surfaces must be created independently from the support.

Black surfaces and text have to be handled separately. Whoever creates the layout must always bear in mind “deep black” objects.

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Creating PDF files After finishing the layout, you still have to create and check the PDF file. But what PDF file should be created? Which configuration is the right one? And when does PDF/X come into play?

To answer these questions we have to clarify where the final transformation of colorimetric space into destination colorimetric space should occur. The two possibilities are the following: • Conversion: In the first case you can convert by means of writing the PDF file in InDesign or afterwards in Adobe Acrobat Pro. In the first method, give the document the desired destination profile through Bearbeiten • Profil zuweisen (Process – Assign profile) (of the printing material). Then call up PDF-Export (native) and select in PDF-Export from InDesign the default PDF/X1-a: 2001 setting. Then go to Register Ausgabe (Output register). The dialog box should look like what is shown in the figure.

All the RGB data is converted to CMYK but CMYK data is excluded from the conversion. This also holds true for CMYK image data with another origin profile. If you want to convert these images too, you have to activate in Farbkonvertierung (Color conversion) the In Zielprofil konvertieren (Convert destination profile) option. This way, now even all the CMYK data with other origin profiles is converted into the destination colorimetric space.

It is also important to know that InDesign flattens all transparencies, so that in certain situations it is no longer possible to convert colors into another colorimetric space! This file is “dead” and can be used solely for the selected destination chromatic space. Anyone who processes this file again or compensates colors becomes a digital “profaner”!

- For the second case, in PDF-Export select the default PDF/X-4: 2008 setting. InDesign thus generates a PDF-Export that is stable from the color standpoint, without reducing transparencies. All the original chromatic spaces and all the transparencies are maintained in the PDF file and the origin profile remains assigned to images. On the basis of this support-independent PDF file, at any time in Acrobat or using a PDF-appropriate tool like callas pdfToolbox, or the color-conversion server from various producers, or inside RIP (Caldera) it is possible to convert colorimetric space into destination colorimetric space. PDF/X-4 data can still be amply processed, and, being support-independent, can be converted even in later years into any X destination chromatic space you prefer.

process - Durst news for screen and digital printers - Issue 69 - February 2011

The digital printer converts as follows: to follow this route, at printing time the printer has to know exactly which color conversion is better and cheaper. In addition, if it uses the latest technology, such as APPE (Adobe Print Engine 2) the digital printer can guarantee optimized transparency processing. The errors that can derive from transparency reduction (whole rows of pixels can be lost) are eliminated once and for all. In this case, as previously stated, whoever created the data must produce a PDF/X-4 through PDF-Export from InDesign.

PDF/X-3 is “dead”.

InDesign can generate a support-independent PDF only with PDF/X-4 because PDF/X-3 doesn’t import transparencies and so they flatten.

And right during flattening, all RGB objects are converted into CMYK! So where does that leave support-independence?

The choice of parameters (compression, text placement, etc,) during PDF/X file creation plays a secondary role where support-independence is concerned. However, even for these factors appropriate values must be used.

Even the way in which special colors are managed has to be treated separately. The point at which special color compensation occurs in the printing material’s colorimetric space depends on the possibilities foreseen by the RIP or instruments available.

Upshot: For the offset or digital printer PDF/X-1a creates “dead” files with color compensation. PDF/X-4 instead creates “open” PDF files independent from the support. It’s that simple.

So try to pursue this path for your own production and bring data suppliers along with you. Only those who constantly follow this road can take full advantage of the possibilities digital printing offers.

The question, from the print supplier’s standpoint, of how to generally manage customer data and which colorimetric space transformations to perform for use in which situations, will be dealt with in upcoming articles.

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