Print Buying Direct

Ever since we started to handle colour images on mainstream computers, colour management of some sort has been a necessary evil. Although one would think it ought to be getting easier by now, there is still room for improvement. The rising number of digital devices in the workflow means that we are dealing with devices such as digital cameras, scanners and monitors that work with emitted light, describing colours in RGB (red, green and blue), but printing them by manipulating reflected light using cyan, magenta and yellow inks. To these primary colours we add black, the key which together with CMY creates the illusion of the other colours we can see.

ICC

Modern colour management largely depends on technologies developed by the ICC (International Colour Consortium), which bridge the worlds of RGB and CMYK using a larger colour space to describe colours, in combination with device profiles. Every device, whatever it is, represents colours uniquely. Different monitor brands and models have slightly different colour fitters and in practice this means that a given colour expressed in RGB values, creates slightly different colours. Black described in RGB has values of zero for each channel because no light is emitted for red, green or blue filtered phosphor guns. Conversely white is created with full signal strength on all channels, encoded as 255, 255, 255 when using 8 bit data per channel for 256 level of grey per colour channel.

Calibration and characterisation with ICC profiles

In order ensure that two different monitors display colours in as similar was way as possible, they need first to be calibrated and then characterised using a colorimeter or spectrophotometer. The second stage, characterisation, refers to the creation of a unique ICC profile for an individual monitor, describing the colours it produces for different RGB-values. The ICC profile comprises a table of RGB values and the colours expressed as a corresponding series of CIElab values. CIElab is the universal colour language, used not only within the graphic arts, but in the most situations where exact colours need to be described.

Calibrating monitors

When calibrating a monitor it’s important to set brightness and white point. Images should then look the same when displayed on a monitor, as when the reproduced image is viewed in a viewing booth. In print publishing, the reference white point is 5000 K (Kelvin), a warm white light which is a compromise between even warmer looking indoor light from bulbs or fluorescent tubes, and slightly colder (bluish) outdoor daylight. The white point of average outdoor daylight is around 6500 K. this is often the reference white in photography, but not in print. The viewing booth at an offset press is set to 5000 K, so if we want to preview an image as it will appear in print, this is the white point we need to use. The brightness level also needs to be matched and in a viewing booth this is between 1500-2500 lux, which is quite an intense light. For a monitor this is equivalent to a brightness setting of around 120 Candela per square meter (cd/m2). Obviously there are challenges when trying to preview images on a monitor, and match the appearance of the printed version, but it can be done. Perhaps not on any cheap monitor, but at least on high end CRT and LCD monitor rs.

Calibrating printers and presses

Colour printers and printing presses are slightly more cumbersome to calibrate than monitors or scanners. The first step is to linearise the printer or printing press. This is basically to make sure that for example 40% cyan really comes out as 40% when printed on paper. On a colour printer this is fairly straightforward to accomplish, assuming you have a function for linearisation in the RIP software.

For conventional printing presses, matters are slightly more complicated, since we have to factor in different dot gain levels for different types of paper stock. Another thing to bear in mind is the ink that will be used. Even thought the ink manufacturer should comply with the ISO standard for ink, in reality individual batches may need to be checked with a spectrophotometer. When correct dot gain values are compensated for in the platesetter, a reference test chart can be printed, and the ICC profile for this press and paper calculated.

Once all devices in the digital imaging process are calibrated and characterised and ICC profiles have been created, colours can be converted back and forth depending on the need and the publishing scenario. This could mean creating a softproof on the monitor, or hardcopy proof on a colour printer. Using this methodology also simplifies the automatic conversions from one print method to another using the advanced functions in modern RIP systems.

When to convert RGB to CMYK

The decision to use a particular paper stock or printing press is often made very late, so is it wise not to perform colour conversions until in the very last minute, since paper and print obviously influence colour. The unconstrained workflow is generally referred to as an RGB workflow. Images are placed as RGB in layout software, and PDF files are created with an assumed output profile embedded, but the actual images remain described using RGB values. By applying the correct output profile in the RIP at the output stage, we minimise the number of colour conversions in the workflow, and ensure that the correct ICC profile is used, taking into account the paper stock and print method used. The layout software, be it InDesign or Xpress, can preview the images even if they are in RGB, by temporarily applying a specific ICC output profile. Adobe Acrobat can also do this for previewing PDF files on screen prior to output.

Spectrophotometer

If properly controlled, a modern, ICC colour managed workflow offers predictability and good image quality, as well as workflow flexibility and tools for production automation. The key is to have the right measuring tools in order to both calibrate and characterise the devices involved. In order to measure total ink density and dot gain you can use a densitometer, but a modern spectrophotometer has this function and does more besides. To calibrate a monitor you need at least a colorimeter, or better, a spectrophotometer and in order to check CTP plates, and linearise the platesetter, you need a spotmeter, because a densitometer can’t accurately read plates.

All modern press control systems use spectrophotometers at the press in order to check that prints really do match the required quality level. The shorthand used to describe colour accuracy is Delta E (∆E), a value that indicates the colour difference from a certain target, expressed in CIElab, and what you actually achieve. A value of ∆E 1 is impossible for humans to differentiate, so we cannot perceive any colour difference and value of ∆E 2 means that the colour difference is just barely noticeable. Depending on the paper stock used the printing method, for most printers an average ∆E value of 4 is considered an acceptable match for quality offset production. For good quality control throughout the print run, the ∆E variation should be monitored and the data saved for later analysis

No-one should claim that colour management is easy to implement, nor to maintain. However, with proper training and using the correct hardware and software it can be done successfully.

For more information on colour management or printing in general please don’t hesitate to contact us at The Printing House (Print Buying Direct)

Adobe’s Portable Document Format, was never designed for high-end graphics art production. Back in the early nineties, when it was first introduced, it was intended for cross platform office document sharing. But the graphic arts industry embraced PDF as a means of transporting content files from point to point, and PDF’s role as the foundation for print media workflows was rapidly confirmed throughout the industry. We should bare this in mind when considering PDF as the preferred file format for print production. There are good reasons for using PDF, but not all PDF files are suitable for output for quality printing.

PDF has become a de facto standard for graphic arts workflows because of its convenience, ubiquity and flexibility. The alternative to using PDF files as the basis for print production is to use either native files, meaning documents saved in the internal file format for the layout software, such as InDesign, Quark Xpress or perhaps Illustrator. We could also export the page content as postscript. But neither approach is ideal and there are benefits and drawbacks with both.

Application files

The problem with sending native files from a designer to a printer or prepress department is that the receiver needs to have the same software installed on their computer in order to be able to open the file. And that software needs to be the exact same version, and ideally running on the same type of computer platform, with the same version of the operating system. As if this want irritating and costly enough, all fonts and possible hyphenation and language modules need also to be in place and of the exact same version, as on the designer’s workstation.

Most layout software doesn’t embed images inside the page document, which is yet another source of possible errors. Instead they have pointers to the high resolution versions of images, which are generally stored somewhere else. This could be on the computer used to originate the file, or on an image server. Working with native files requires all of these variables to be taken into account, for the files to flow through production without mishap. Missing images or missing fonts, or both, are among the most frequent errors in prepress troubleshooting. These are all reason to work with PDF, where all file components from images to colours can be contained within a single file. It’s clear that PDF has mostly replaced Postscript as the preferred page description language. PDF files are easier to work with and less cumbersome to handle in print production than native layout document files from InDesign or Quark X Press. Preparing documents for print will perhaps never be childsplay, but using PDF files in general, preflighted and well prepared PDF/X files in particular, is the path to better, more secure file processing.

For more information on providing us with PDF files please don’t hesitate to contact us at The Printing House (Print Buying Direct)

PREPARING TO PRINT

Once the layout and design of a job is complete, you’ll need to decide how to hand over your files. At The Printing House (Print Buying Direct) we usually prefer a single PDF but can work with all of the source files.

Either way, you’ll want to run though a preflight checklist. For more information see our artwork guidlines webpage.
PREFLIGHT CHECKLIST… ARE YOU READY?

• Ensure that all graphics and images are in their final size and correct resolution, 100% at 300 dpi.
• Rotate, scale and edit images and graphics prior to placing them in page layout applications.
• Image file formats should be EPS or TIFF (not JPEG) and verify that all source files are linked properly.
• All spot colours should be designated as spot colors and not as CMYK recipes.
• Spell check your document.
• Remove any trapping (allow the printer to apply trapping).
• Check for transparency and either flatten or notify the printer so they can flatten the file. All bleeds should generally be set to 3 mm.
• Gather all source files: fonts, graphics, images and layout documents, if requested. Use the [Package] feature in InDesign or the [Collect for Output] in QuarkXPress.
• Perform a visual preflight using overprint preview, colour separations preview and transparency flattener preview.
• Prepare a mock-up to give the printer as a finished sample.

TRAPPING

• For best results, trapping should be applied by The Printing House and not the yourself. Trapping settings made in the application are not included in the PostScript when printing with the Composite mode.
• Avoid instances where trapping to gradients or images is required (the change in color may not reproduce well).

BLEEDS

Include 3 mm bleed for all areas that extend off the page when trimming is required.

IMPOSITION

If you plan to use binding, leave ample room for the gutter. Aside from that, we will do all imposition work.

INDESIGN CS2 PREPARE TO PRINT

PREFLIGHTING

• Use the [Preflight] feature under the File menu to make sure all fonts, graphics and image links are present.

PACKAGING

• Use the [Package] feature under the File menu to collect all fonts, graphics and images used in the job. This will ensure that all elements are collected when the job is delivered to The Printing House. Instructions and contact information can also be included by the designer for us.

QUARKXPRESS 6.5 PREPARE TO PRINT
USAGE…

• Use the [Usage...] feature in the Utilities menu of QuarkXPress to review that all fonts, graphics and images are linked correctly in the file.

COLLECT FOR OUTPUT

Use the [Collect for Output] feature in QuarkXPress to gather all fonts, graphics and images used in the job. This will ensure that all elements are collected when the job is delivered to the print provider. Note, however, that you will need to gather fonts from imported EPS or PDF pictures manually unless they are already imbedded into the EPS or PDF file.

ACROBAT DISTILLER 7 SETTINGS

• Create PostScript from the source application using the Acrobat Distiller PPD.
• Be sure to use the Binary data format and include all fonts.
• Use the Smooth Shading feature in Acrobat Distiller.
• The Save As features in PDF Writer/Maker or the Mac OS X Save As PDF feature should be used with caution.

The following recommended settings have been optimized for high image quality printing. In some instances, productivity may take priority over image quality and, therefore, require different settings (such as adjustments in compression).

Open Acrobat Distiller and go to the Settings menu. Select [Edit: Adobe PDF Settings...]. Create a custom set choosing the following recommended settings and select [Save As...] using a new fi le name (e.g.,“ artwork for The Printing House”).

Distiller will save the file in the right place so it can be accessed as a new Job Option set.

• Select Acrobat 6.0 ( PDF 1.5) for the best compatibility. Note that since you are working with a PostScript file there is no need to select Acrobat 4.0 compatibility for transparency concerns (writing files to PostScript always flattens any transparency effects).
• To ensure that the orientation of the pages prints correctly, do not select the Auto-Rotate Pages feature.
• Embed Thumbnails is optional. Versions of Acrobat 5 and higher are able to dynamically create thumbnails on the fly.

IMAGES

To preserve the best image quality, compression is generally not recommended.

Distiller 7 contains a new Policy button. You will need to decide the threshold of what level of resolution is appropriate for the quality of the job and if the job should pass, fail or warn the user. Try setting the minimum as 200dpi and the max as 400dpi.

FONTS

• If jobs fail while distilling, check the job for missing fonts. The following settings recommend cancelling the job when fonts are missing to ensure the document prints correctly.
• To guarantee the font information is successfully included in the Adobe PDF file and will view properly on the monitor, the required fonts should reside either in the system folder of the computer or in the PostScript file.
• A higher percentage value is generally recommended for [Subset embedded fonts . . .].

COLOUR

• The Settings File selection under Adobe Colour Settings should usually be set to [None], [Leave Colour Unchanged].

ADVANCED

• The Convert Gradients to Smooth Shades feature can help smooth vignettes/ sweeps/ gradients with Vector-based programs such as Adobe Illustrator or QuarkXPress. Using this feature with Microsoft Office jobs may or may not improve the job due to the way sweeps are generated in those applications.
• As a precautionary measure, use the Save Adobe PDF Settings Inside PDF File feature. The recipient of the PDF may be able to troubleshoot problem files more easily if the settings are included with the job.

EXPORTING PDF FILES

When exporting files from InDesign or QuarkXPress, you can apply many of the same Acrobat Distiller recommendations discussed previously.

INDESIGN CS2—EXPORT PDF

The PDF options for InDesign are fairly similar to those in Acrobat Distiller. If there is a custom set saved from Distiller, it will be selectable from the PDF Export dialog box. Follow the settings previously discussed.

There is one additional group of settings, [Marks and Bleeds], that can be set to your preference.

QUARKXPRESS 6.5—EXPORT PDF

In QuarkXPress be sure to click on the [Options...] button to access all of the available controls over PDF settings.

You will want to check the options under the Job Options and the Output tab. Take special care to ensure the Color [Output Type] is set to [Composite] and that [Print Colors] is set to [As Is].

Note that blends made with PANTONE® colors in Quark 6, will print as RGB when the [Print Colors] selection is set to [As Is]. To preserve PANTONE Blends (gradients), set Print Colors to [Device N]. Using [Device N] will, however, convert any RGB text, objects and images to CMYK.

PREFLIGHTING PDF FILES

In Adobe Acrobat 6 or higher you can use the Preflight tool to create your own custom preflight profile or use one of the default profiles. If you are not familiar with this tool you may want to talk with your print provider first. They may be able to provide you with a customized profile or walk you through the process.
Also refer to the Adobe documentation provided with Acrobat.

For more information or help please call The Printing House (Print Buying Direct) on 0870 950 8444

The Printing House Ltd – Marshfield bank, Crewe, Cheshire, UK

Transparency features in graphics applications allow users to create elements with drop shadows, overlays, blends and feathering. Because transparency effects can be complex, be sure to consult us for best results. But the following notes should point you in the right direction for getting your artwork ready for print.

TRANSPARENCY IN ADOBE ILLUSTRATOR

• Select [File: Document Color Mode] and choose [CMYK Color].

• Set the [Effect: Document Raster Effects Settings] Color Model to [CMYK] and the Resolution to [High (300 ppi)]. Any effects that require rasterization will use the value specified here.
• Use the Transparency palette and [Effect] stylize menu to control transparency effects. Note that [Filters] can produce unpredictable results.
• The [File: Document Setup: Transparency: Preset] should also be set to [High Resolution].
• The Flattener Preview palette [Window: Flattener Preview] can identify areas that have transparency applied or are effected by other objects.
• Be sure to enable [View: Overprint Preview] for the most accurate display of what the fi nal design will look like.

TRANSPARENCY IN INDESIGN

• Select the [Edit: Transparency Blend Space] to [Document CMYK].
• Use the Transparency palette to control transparency effects.
• The Flattener Preview palette [Window: Output: Flattener Preview] can identify areas that have transparency applied or are effected by other objects.
• Be sure to enable [View: Overprint Preview] for the most accurate display of what the fi nal design will look like.

PRINTING WITH TRANSPARENCY

• In the printing or exporting windows always select [High Resolution] for the Transparency Flattener.
• Printers often define flattening settings or flatten artwork themselves. Consult your us to determine if your work should be submitted flattened or with live transparency. Note that transparency effects will always flatten when printing to PostScript or EPS, or if they are exported using the Acrobat 4 (PDF 1.3) format. Transparency effects will remain “live” only if exported using the Acrobat PDF 1.4, 1.5 or 1.6 formats.

CAUTIONS

• Use spot colors in transparency effects with discretion. When spot colors contact CMYK objects with transparency, the best practice is to make sure they are on the top of the stacking order.
• Avoid transparency designs that contain both RGB and CMYK content.
• QuarkXPress 6.5 does not have built-in support for transparency.

If in any doubt call us on 0870 950 8444 or contact us through either of our websites – Print Buying Direct or The Printing House Ltd, Crewe, Cheshire, UK