This document aims to clarify the difference between “Regular” printing in the LFP world with the newer concept of “Standardized” printing.
Both concepts will be explained, as concept, but also how to actually do it in PrintFactory.
- Input profile
A profile either embedded in a file or image, or assigned to a file or image prior to color conversion through ICC profiles
- “Reference” profile
A profile of a “Reference” device. Currently the whole graphic industry accepts and promotes ISO Coated v2 as a standard, or “Reference”.
- Printer profile
A profile of a printer or other output device. This profile contains besides an ICC profile also linearization and ink limiting information.
- Render Intent (RI)
The way out of gamut profiles are treated during color conversions using ICC profiles. More information can be found here or here.
A PDF standard, which includes a series of printing related requirements. One of these requirements is that the printing condition or “Output intent” needs to be specified, in the form of an ICC profile (e.g. ISO Coated v2 or SWOP). There are several PDF/X “levels” from X1a to X4, specifying extra items as spot col-ors, other color spaces then CMYK, transparencies and profile embedding.
A PrintFactory RIP queue is a parameter set, which defines what will happen with files sent to it via Editor or via drag and drop on the queue. A queue can publish itself as a printer which can be shared on the network and is also a hotfolder. Files dropped in the hotfolder will be processed by the RIP with the pa-rameters set in the respective queue. Typical parameters in a queue are input and or reference profiles, printer profile, some layout settings, etc…
- PMM (Printer Media Mode)
The PMM method allows printing to the RIP without any queue created on the RIP. Instead the RIP scans the profile folder and publishes the profiles sorted via Printer type, Media name and Mode name. This makes it easier to navigate when having multiple printers. It also allows to transfer all the color controls to the PrintFactory Editor. It will then control how colors will be converted and to what printer and media the job will be sent.
A profile that converts a device space (like CMYK) directly to another device space without using CIELab of XYZ as intermediate connection space. A device-link is capable of optimizing the conversion from the input space (reference) to the output space (printer space) as during the calculation it is for example known which percentages are forming the grey axis and thus being able to preserve it. Because it does a single calculation (CMYK > CMYK) instead of a double calculation (CMYK > CIELab > CMYK) it is more accurate.
Generally speaking there are two ways one prints in LFP up to today:
- Using color management
- Not using color management
A RIP is almost always setup with printer profiles. These contain ICC, linearization and ink limits. When also input profiles are set up, files or images will be tagged with the respective profiles (RGB images with RGB in-put profiles, CMYK with CMYK profiles, etc…) and converted to the ICC in the printer profile using the RI set in the preferences. This means the color values are converted to achieve an as close as possible match to the input colors, taking into account the limits of the printer.
Problems that can occur with this method:
- Color differences
Color may look different because the input profile might not match the profile the designer used/assigned. For example when an image with text on top is processed and the text color is derived from a part of the image, changing the profile or intent with the image changes the color of the image relative to the text, not intended by the designer. Applying different profiles and or render intents to different elements (images and vectors for example) can seriously affect the appearance. Again the example where a text is set on top of an image, if the text is rendered with the AbCol RI and the image using the Perceptual RI, differences occur that were not in-tended.
- Overprints, transparencies & blends
These elements can dramatically change when applying profiles. For example an element which after con-version to ISO Coated v2 would result in C+M, but converted to the printer profile result in C+M+ a bit of K, underlying text in K would disappear, since in the latter case also K was generated. Also with transparencies color differences can occur since elements that would blend are maybe converted using a different RI. So overprints can “disappear” and blends can look different when assigning profiles.
- Perceptual Intent
Since perceptual intent changes all the colors in the file, not only the out of gamut ones, colors might look very different depending if you convert to a standard like ISO Coated v2 or to the printer profile. Next to the same job printed on different printers will look very different, since the gamut of the different devices can differ a lot and the Perceptual intent adapts all the colors to the output profile.
- Spot Colors
Non defined spot colors are printed using the alternate space (mostly CMYK). If the designer has taken that into account, the result might look very different due to the same reasons as explained in item 1.
Figure 1a shows the output of a document created using Adobe Illustrator and consists of an image (RGB with embedded sRGB profile). a grey background (sampled from the background of the image). a text with a color sampled from the acorn and gradient again from that color.
Figure 1b shows what happens when the ‘Designer’s Intent’ is ignored. The designer’s intent is usually unintentionally and depending on the (default) settings of the application that defines the CMYK that is used to work in.
- A color difference appears as the background is defined in CMYK without a profile. Adobe Illustrator defined the CMYK from the grey of the (s)RGB image (acorn) by converting it to SWOP (the working space the designer has set-up). If not exactly that combination of profiles with the right rendering intents is assigned to the image and the background a color difference will appear.
- The color of the acorn became brighter and more saturated compared to the rest of the design because it is mapped directly to the printer gamut. This is what you expect that is wanted but as can be seen it breaks the match with the other colors (like the text and gradient) in the design.
- The gradient is defined by an overprinting spot color. As the background has now 2 different appearances (see #1) this is also seen in the overprinting or blending effects.
Figure 1c shows what happens when spot colors are removed or replaced with RGB or CMYK before RIPing or when overprint is switched off (as a method to counter issue 3 in figure 1b).
- The text is no longer overprinting as its color has been replaced with a CMYK that is representing the spot color. The CMYK used was a very accurate match with the spot color but due to the overprinting effect the spot color was darkened by the grey background.
- The gradient is no longer showing the correct overprinting effect. As the spot color before was a duo tone fading to 0 of another spot color and as a result it nicely blended away. But due to either switching of overprint or by replacing the spot colors with their matching CMYK equivalents the overprinting blend has been lost and it blends to white.
Conclusion of this example is that any change to the original design by assigning/removing embedded profiles, disabling overprints or replacing spot colors before RIPing (and thus blending) results in broken output.
Not using color management sends the file’s CMYK data directly to the printer, only passing via linearization. This method results in the least color consistent prints and is not recommended.
The goal of Standardized printing is to reduce the color deviations and variations in prints produced from different printers. These differences exist because these machines vary in color capabilities, sometimes quite drastic. This is due to the variety of printhead technologies (Piezo, Bubblejet), inks (Solvent, UV-curing, mild or ECO solvent, dye and Latex) and substrates (paper, PVC, vinyl, PE, PET, …).
Next to that the standardized printing method respects the designer’s intentional overprint, transparency and blend effects. They are converted correctly to the output intent or reference before converting to the printer.
This means that by doing nothing the output is correct and utilizing everything the gamut of the printer has to offer. So no experiments on the printer to see if the job is right as it is always correct. Saving operator time in preparing the job and printer time testing the job.
The way this is done is to convert all incoming (non-CMYK) color spaces to a chosen Reference profile and then to the printer profile. This way all the colors get matched to the standard or reference, and then converted to the printer’s capabilities, maintaining the overall color appearance between different devices.
PDF/X has been developed (among other reasons) for this. It contains the output intent (Reference) with which it should be processed. Next to that, from PDF/X3 on, all file elements of a color space which is not equal to the output intent’s color space need to be tagged with an ICC profile, to assure correct conversion to the output intent can be guaranteed.
As all modern applications support PDF/X it is very easy to specify how your customer needs to supply its job; Choose Export and Select the highest PDF/X that is specified. It delivers a single job with everything embedded and can very easily be checked if it is acceptable for print.
The standardization converts all color elements to a single color space (reference profile) and spot colors. This allows the unambiguous use of device-link profiles as there is only one color space after standardisation. The use of device-link profiles allows PrintFactory to calculate a direct link and thus delivering:
- Neutral grey
As the reference space is known it is also known what the grey axis is and the device-link can be optimised for that.
When working through CIELab the source of a dark color is unknown, there are several CMYK combinations that lead to similar CIELab values. As with standardization the separation of the reference is known it allows to optimise the device-link profile and keep very nice defined mid- and dark tones open while saving significant amounts of ink.
Saving ink is delivers a direct benefit due to lower ink costs and has additional benefits like; prolongs longevity of heads, improves printability on media and allows to use lower temperatures which printing.
- Tuneable profiles
The device-link knows which targets it needs to achieve and how to get every individual printer back to its golden state. This delivers the possibility to print a relative small target (approx. 500 patches for a CMYK printer) and read it with a spectrophotometer. After this measurement step the software simply presents a pass or fail. If it fails it knows how to correct for the deviations and adjust the profile. This process is a simple print-and-measure step so every operator can perform it without additional color management training.
An often heard story is that using a reference space will limit the capabilities of the printer to the intersection of the reference gamut and the printer gamut.
This is not necessarily so as there are several strategies that can be used and all have to do how the job is handled after the standardization process:
- Spot colors
In traditional offset the limitations of the gamut are lifted by introducing spot colors. This is also the common way designers work and as a result most of the jobs already contain spot colors for the company colors or where the designer felt he/she was limited by the working space (=reference).
The spot colors are rendered along the reference space and not compressed in it. So a job using ISO Coated v2 as reference and two Pantone colors will actually render as a 6 channel job; CMYK + Pantone 1 + Pantone 2. This method ensures that all blending and transparency effects are correctly done (like drop shadows and overprints) while enabling the RIP to address the full gamut of the printer with the result.
- Gamut mapping
If printer to printer consistency or a match to a contract proof is not the preference but punchy colors are then the resulting reference colorspace (usually CMYK) can be mapped to the printer gamut in anyway you like. So if the printer gamut is larger a perceptual mapping with black point compensation will make the reference space expand to the maximum of the printer gamut. Equally true if the printer gamut is smaller, but in that case a hybrid between perceptual and colorimetric is recommended; keeping colorimetric in the middle of the gamut (the achievable part) and perceptually compressing the gamut on the edges to retain a visual comparable product without introducing flattening of colors at the edge.
For fine-art and photography a RGB reference can be used. This delivers a large gamut without unnecessary separation to a reference CMYK where the black generation of the reference might cause breaks in the smooth transitions. After that standardization to RGB using the aforementioned gamut mapping of your liking the result can be mapped to the printer gamut. While still enjoying both the benefits of standardization and device-linking.
A common remedy for color differences in the files or ‘broken files’ is to open the file in Adobe Photoshop and let Photoshop flatten it completely to CMYK. This does work as it correctly respects all elements and thus the designers intent.
This approach has the following downsides:
- Photoshop also renders the spot color to CMYK it dulls down the spot color of the references gamut and removes control over the spot colors (tuning, replacement, etc.)
- The document needs to be flattened to a sufficient resolution at output size, this results in a large files and time consuming operations.
Another common alternative is to use a ColorServer front-end before the RIP. A ColorServer does deliver you all the benefits of standardization printing.
Even though especially designed for this job there are some downsides on using a ColorServer:
To be able to process all color conversions parts of the document needs to be flattened to image. The more complex the document is the more flattening occurs. This process often require quite a bit of processing and results in uneditable (as partially flattened) and bulky output files which make the following steps in the workflow slower and more error prone.
If the collating/gang and job preparation has been done before the ColorServer then complex files are presented to the ColorServer bogging it down due to its complexity.
- Room for error
The job processed by a ColorServer requires a specific set-up at the RIP to avoid further color processing and only linearisation is applied. Also each conversion type requires its matching set-up at the RIP. This results in a complex set-up that is hard to maintain and is easy to break or when jobs are processed manually in a big risk of human error or a combination of both.
- Spot colors
Depending on the capabilities of the ColorServer, also the spot colors might be flattened to the reference space and thus being dulled down and removing control over them (spot color tuning, etc.)
EPS is still very popular as a file format for delivering LFP jobs as it is, unintentionally, delivering standardization of the job. EPS is a format based on PostScript and therefore has limited capabilities compared to PDF (PDF is the successor of PostScript). It lacks blending, transparencies and advanced color management therefore all Adobe applications perform a lot of flattening of the file and thus removing all risky elements.
Using EPS is strongly discouraged because:
- EPS needs to be converted to PDF using a Distiller prior to processing and thus adding a lengthy preprocessing step.
- Files are commonly many times bigger and heavier than PDF as all smart PDF elements have been replaced by dump and heavy images.
- The images used for flattening are at a fixed resolution, thus scaling the output can lead to jagged output.
- Resulting PDFs are uneducable and are hard to touch-up as many elements are cut in many smaller pieces during the flattening.
PrintFactory delivers an integrated approach combining standardization printing and device-linking in one seamless workflow. Due to a deep integration and moving all the processing to a single moment as last step in the workflow it delivers both an easy to use, reliable and fast solution on doing this.
- Reduce human errors
The standardization workflow is integrated in each component, being it either the Editor, Layout, RIP or Calibrator. It is the default way of working and no additional actions have to be taken to make it work. standardization allows to stays away from making many settings and decision and as a result reducing the possibility for human error and reducing the amount of hours needed to prepare the job.
The same PDF engine that is used in the RIP is also used in the Editor and Layout to preview the jobs so they will always look the same. Every view is a live preview including live transparency and overprint with a soft-proof of the actual printed result because all settings and properties are automatically retrieved from the printer through the zero-conf network.
- High performance
The heavy lifting is done as last at the RIP. The RIP does collating/ganging, rendering (the actual RIPing), color management, bleeds, folds, white generation and many other tasks at the very last moment in 1 go. Until that moment the job only consist of the PDF and XML instructions for the RIP allowing to make last minute changes but more importantly avoiding creating complex and heavy intermediate files that become heavier and complexer after each operation done on them. Combining all this in the last step makes it both fast and reliable.
- Device-linking on the fly
PrintFactory Calibrator does not create a conversion tables after it measured the targets. The linearisation, ink splitting and ink limits are set but no profiles are created. The first RIP in the network that encounters a specific reference profile, media and printer combination for the first time for a particular printer will create a profile on the fly based on the setting set the operator has send (called Variation). So there is no need to create extensive sets of profile variations up front only to find out that a specific variation was not done.
How to use it
PrintFactory Editor will allow to work via the principle of Standardised printing. This can be done in different ways.
- The job is a PDF/X (any PDF/X type)
- The job is a regular PDF or other file format
The job is a PDF/X
If a job is PDF/X, PrintFactory Editor will detect the output intent and set it as output in the Channels palette. All color elements in the file will be converted to this output intent on the fly, using the embedded profiles and rendering intents (RI). Example is the Altona Visual, this contains various elements in RGB, Lab, Grey and CMYK. All non-CMYK elements are tagged with profile and RI, specifying the conversion to the output intent or reference. While the output tab of the Channels palette shows the resulting CMYK values, the input tab still shows the original RGB, Grey and Lab values from where the CMYK is calculated from.
When a PDF/X is opened, the output intent is automatically detected. When printing (producing) the job, in the “Submit job” dialog the option PDF/X intent needs to be set to Relative Colorimetric or Perceptual, depending whether the printer’s gamut is smaller (Perceptual), equal or bigger (Relative) than the output intent.
When doing so, the input colors other than CMYK will be converted to the reference, resulting in a CMYK file, this file is then flattened and converted to the printer’s color space with the output intent as the reference profile.
The spot colors that are present in the file are mapped directly to the gamut of the printer without being converted first to the reference CMYK. Therefore it essential to respect the spot colors and overprints otherwise the blending might break (ref. figure 1c)
The job is a regular PDF or other file format
When the job does not contain an output intent the reference profile is set as defined in the Standard Preferences and the profile selected at Print Standard will be assumed.
If the above preference is not set then the user needs to choose the reference profile from within the Channels palette. Clicking the button will open the “Choose profile” dialog where a CMYK reference profile can be chosen (ISO Coated v2 in this example).
The rest of the procedure is identical.
Setting up PrintFactory
- Ideally the PrintFactory RIP should not contain queues. Printing via PMM is simpler and can be less confusing than working with queues.
- In the color preferences of PrintFactory Editor, choose “Never” with the “Apply on open” choice. This leaves the document as-is, meaning that embedded profiles will stay embedded, untagged images or elements will stay untagged. Alternatively you can choose “Leave untouched” and check “Never ask again” in the “Color management” dialog which appears when opening a job.
When opening files, make sure the color management settings are done as described above.
- If the file opened was a PDF/X, you will see the output intent selected in the output tab of the Channels palette.
- If the file was not a PDF/X, click the button in the output tab of the Channels palette and select ISO Coated v2 in the CMYK profiles list.
- Proceed with all the job preparation that needs to be done like scaling, paneling, grommeting etc.
Printing/producing the job
When the job is prepared and ready to be printed, choose File>Production to enter the Production dialog. In the first tab, select Colorimetric or Perceptual in the drop down list with the “PDF/X intent” choice.
Then proceed with the other settings and click the “OK” button.
There are some things to keep in mind when using Standardised printing in PrintFactory:
- The ink values in the Output tab of the Channels palette are the values of the conversion to the Reference profile set (e.g. ISO Coated v2) and are not the ink values the printer will lay down.
- It is not possible to control the exact ink values on the printer using the “Device Space” option in the “Style” palette.
- Spot color reproduction in printer inks can not be done directly from the Editor, since the CMYK values seen are of the reference profile, not the printer profile. Spot colors need to be defined in the Calibrator (where it is also possible to do this in printer inks).