Troubleshooting Color: Output Color Profiles

More than once I have been asked: "OK, so the color is wrong, how do I make it right?"

Troubleshooting CMYK color can be a pain, because there are often many places the problem could be lurking, and changes made in one, may inadvertently alter the output based on info from another. So in this five part series, we will look at five important steps to troubleshooting a color managed system, or colorimetric tuning.

As you all know, a color management system is usually broken into five parts:

1. Source color space
2. Media parameter setup
3. Source color space designation
4. Output color profile
5. Output calibration set

Let's take a look at number four on our list - Output Profiles

One of the first things to be aware of is your own expectations. People often assume that printer profiles should make everything match but a printer profile is just a measurement of what a combination of printer, ink and paper can reproduce.

Different types of printers and ink sets will produce different color gamuts. Different papers and surface textures will influence both color gamut and appearance. Matte papers always look flatter than gloss papers for example. Also the color of the paper white has a big influence. A warmer paper color will give warmer grays and skin tones than a cooler more blue-ish white paper.

Media with Optical Brightening Agents (OBAs) often require custom profiles to account for the fluorescing factor.

The combination of the ICC output profile and the calibration set allow the RIP to adjust for the white point, imaging characteristics and d‐max capability of the output media. For standard color, the output profile may have less effect on color than does the calibration set and other factors described previously. Bypassing conversion always ignores output profiles.

In most cases, the standard Fiery output profiles for Plain, Coated Matte & Coated Gloss may be suitable for most customers on most media. These are based on GRACoL standard, therefore are neutral grey by default.

After machine setup and linearization, the machine should be calibrated on the target media and test prints made using the applicable standard Fiery profile. Only if results appear unacceptable or sub-optimal should the time be spent to create custom output profiles.

If a custom output profile is necessary, the standard 928 patch target seems to provide suitable results on most printer/copiers. I advocate the use of an iSisXL spectrophotometer to reduce the time and effort to read the test patch pages. Otherwise, an ES‐1000 or ES‐2000 can be used within a Fiery RIP, or an XRite spectrophotometer for external software, but of course, using a hand-held device takes more time.

In some cases, the profiles being used in Photoshop may not be the same as the profiles on the RIP controller. One example of this is if the USWebCoatedSWOP profile is being used in Fiery Creative Suite with a newer RIP controller that has the SWOP2006_Coated3 profile installed from the factory. In these cases, you may import the profile you are using for the working space definition in Creative Suite onto the RIP's controller so it is available in Color Setup.

Another example is if you are using a custom press profile for a conventional press and need to match the RIPs color output to that press.

If your inkjet is driven by RIP software then part of the calibration and profiling process is setting the printer options, ink limiting and linearization and it is with these that the root of most problems can be found. Getting the printer options right for any media can take a while, factors such as the number of passes, resolution, head height and drying times all can have a big influence on the print. Again the media manufacturer should be able to guide you.

Specific settings that may help:

Optimized: Creates custom calibration d‐max calibration targets as read from the profile test patch page(s). 
This setting should generally be left ON, which is the default for most printer/copiers. Only the d‐max endpoint is read from the target. The intermediate curve is calculated using a general formula and does not follow any unique density variations in the printer/copier.

Black Generation: Specifies toner limit and GCR parameters. 
Specifying a black toner maximum of 95% instead of the default 100% will provide a smoother tone and gloss generation in the deep shadows. If designated at 95%, TAC reaches a 180‐260% value in the shadows, while designating at 100% usually causes a TAC drop to about 130%. Using the 95% black specification prevents a gloss roll‐off in the shadows on some media, while using the 100% black specification may reduce total toner usage. 

95% is usually recommended for best image quality. A TAC (Toner Limit) value of 260% should be used. Default values for Ricoh printer/copiers in CPS Ver 3 and Ver 4 may default to either 400% or 270% dependent upon the revision. 

Very aggressive GCR settings may reduce banding and total toner usage dependent upon the colors found in the source job. Changes to other parameters may be used for specialized purposes.

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Do you have a color management question, horror story or event to share?

Email me at reilley4color@gmail.com

Troubleshooting Color: Source Colorspace Designation

More than once I have been asked: "OK, so the color is wrong, how do I make it right?"

Troubleshooting CMYK color can be a pain, because there are often many places the problem could be lurking, and changes made in one, may inadvertently alter the output based on info from another. So in this five part series, we will look at five important steps to troubleshooting a color managed system, or colorimetric tuning.

As you all know, a color management system is usually broken into five parts:

1. Source color space
2. Media parameter setup
3. Source color space designation
4. Output color profile
5. Output calibration set

As we have discussed, the source colorspace is crucial to determining how the system should translate from the input color to the output color, via command given to the rendering engine. Without knowing where you start from, it is difficult to navigate where you wish to be.

The color space and variant used to create the job must be designated in the RIP's job parameters. If you know with certainty the input color space, you can define it explicitly. If you do not have this information, most operators use sRGB, since it is the smallest of the RGB input color spaces, and thus the lowest common denominator.

Most RIPs allow you to recognize if a given file has input profile information embedded in the file. If present, this information gives you the best chance of output that matches what the file's creator intended.

Almost every file has some CM information present. Even if the original creator of the file was not prepress proficient, Adobe Creative Suite automatically embeds color input info when saving files. Should someone convert from RGB to CMYK in Photoshop, for example, the file is now in GRACoL CMYK, since that is Adobe's default. Honoring this embedded information is the best way to ensure you are printing to the original creator's intent. It is up to the operator to ensure that this embedded data gets honored.

The easiest and most consistent way to do this is the Use Embedded Profile When Present selection in the color setup tab of the job's parameters which is only effective when the job contains an embedded tag/profile. This is usually the first item to check when printed colors are significantly different than expectations. 

A few troubleshooting hints:

• AdobeRGB jobs printed as sRGB appear flat.
• sRGB jobs printed as AdobeRGB appear too dense with high chroma.
• Flesh tones in GRACol/SWOP jobs printed as ISO (System 7 default) appear rather sun burnt.

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Do you have a color management question, horror story or event to share?

Email me at reilley4color@gmail.com

Don "Hutch" Hutcheson Interview

With more than 41 years of experience in photography, design, prepress, printing, and color science, Don Hutcheson has pioneered many techniques we now take for granted, like RGB workflows, soft proofing, extended-gamut printing, and digital proofing.
In 1995 he started the world’s first color management consultancy, HutchColor, LLC, to bring the concept of ICC color management to professional graphic users. Today he continues to train the world’s top printers, publishers, agencies, photographers, and designers through private consulting and public conferences.
In 2006 as chair of the IDEAlliance GRACoL Committee, Hutcheson used his own proof-to-press calibration method (now known as “G7®”) to produce the current GRACoL and SWOP data sets. Since then G7 has made standardized printing and proofing easier and more accessible to thousands of printers and print buyers world-wide.

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CR:     Let’s start with a bit of history. How did you first come to be interested in digital color, and what kind of training prepared you for the career you now have?

DH:     Digital color is the child of desktop publishing, which evolved from electronic color scanning, which in turn evolved from graphic arts photography or “color separation” – one of the key enabling technologies in the development of color printing. Like all printing, digital color is therefore simply a form of photography, which has been my passion since I was 13, so its natural that I should be interested in it.

From 18 thru 22, I served a five-year apprenticeship as a graphic arts camera operator at a company called Photo Engravers, Ltd. In Auckland, New Zealand. When they bought one of NZ’s first electronic drum scanners – a Hell C-296, the union wanted it to fail and put me on it with nothing but a badly-translated German manual.

I twiddled every knob and made every mistake you can imagine, including one day removing all the unwanted inks and replacing them with black. When that job hit our 1-color proofing press a few days later, it was like nothing anyone had ever seen before and I was nearly skinned alive, until they added the black plate, when suddenly everything looked wonderful. Today we call that GCR.

Though designed for CMYK work, I saw the scanner’s photographic potential and found I could make just three RGB negatives and print them onto photo paper through RGB filters. With a little experimentation I was able to make prints that matched not only the color of an original transparency, but also the subtle highlight and shadow details with a level of perfection hitherto unobtainable by analog means.

Although the C-296 was not a digital scanner, it was my first experience of what we now call digital imaging and I’ve been hooked ever since.

CR:     Your career has spanned several decades – what are some of the technologies that have come and gone during that time?

DH:     Continuous-tone camera separations, direct-screening camera separations, tray development, nitrogen burst development, glass screens, contact screens, silver masking, tri-pack masking, double-overlay masking, wet etching (with potassium cyanide!), dry etching, film stripping, ruby masking, analog proofing (AgfaProof, DuPont Cromalin, DuPont WaterProof, 3M Color Key, Transfer Key, and MatchPrint, Remak, etc.), drum scanning – you name it.

CR:     Is there any technology or ideology that has faded from use that you might hope we re-discover? Or what might be the next bleeding edge tech in the world of color management?

DH:     I’ve always loved the early continuous-tone printing methods like Collotype, partly because there are no dots to interfere with fine image detail, but also for their purity of color. Halftone printing imposes some color space limitations that don’t exist in true continuous-tone printing, where ink film thickness is varied rather than dot size. If someone invents a practical way to print truly continuous-tone CMYK with offset or digital efficiency, it will have a dramatic impact on fine-art reproductions and expanded-gamut applications.

As for the bleeding edge of color management, today’s biggest challenge is the huge difference between the official D-50 illumination standard and the actual light sources in viewing and measuring equipment. Color management is based on the assumption that we can measure color as it is seen by the human eye, but we are far from achieving that to a high level of accuracy.

The problem lies in the D-50 standard itself, which defines the quality of “standard white light” as a graph of emitted energy vs. spectral wavelength. Unfortunately, the D-50 spectrum is based on hypothetical “daylight”, rather than any commercially-available light source, so D-50 can only be crudely approximated by today’s viewing and measuring equipment. This means certain inks, dyes, papers, etc. can measure quite differently than they appear in a so-called D-50 viewing booth, and often an excellent “measured match” (with effectively zero delta E) can look unacceptable visually, and vice-versa. This disconnect between the D-50 standard and real-world light sources becomes even more of a problem as the demand grows for ever-higher standards of measurable color accuracy.

The obvious solution is to replace the D-50 standard with the spectral curves of a commercially-available light source, such as the fluorescent tubes used in today’s viewing booths, or some new LED equivalent, but agreeing on a new light source is fraught with political, economic and patent issues. Meanwhile, there are work-arounds that can reduce or eliminate the problem, but because they deviate from the D-50 standard, they are difficult to implement en masse. The new M1 measuring standard solves part of the problem but is far from a complete solution, and has in many cases exacerbated, rather than reduced, the related problem of OBA-enhanced papers, which fluoresce under UV light.

CR:     Let us now discuss the G7 protocols and their evolution – can you walk us through some of the early days of G7?

DH:     Around 1980 I developed a simple way to calibrate a color scanner to match the tonality of one printing or proofing system on another. At the time, “Dot Gain” (now called “TVI”) was the accepted basis for press calibration, but I found that consistent dot gain failed to give consistent visual appearance with different press conditions or technologies, like offset and pre-press proofing.

To solve the problem, I developed a simple neutral density-based technique that achieved a perfect visual match on neutral grays, regardless of inks or technology. But if the dynamic ranges of two devices didn’t match, I had to tweak the graphs to meet at the shadow point, while keeping highlight regions identical. That “shadow compression-expansion” principle remains one of the key features of G7, and the technique I used back in 1980 is still alive today in the free G7 Graph Paper Method.

Fast-forward to the 1990s when CtP removed film from the plate making process and the question became “what do we calibrate?” Previously we linearized the scanner or film setter, but now you couldn’t do that. So I put my 1980’s method into an Excel spreadsheet that allowed any press to match the tonality and gray balance of any printing or proofing system, and called the process “P2P” for proof-to-press or press-to-proof.

In 2004 the GRACoL committee used the P2P process to help develop the new GRACoL 2006 color space. We followed all the ISO 12647-2 rules except the obsolete TVI curves, which we replaced with NPDC (Neutral Print Density Curves) averaged from a number of ISO-standard press runs made with un-calibrated plates. The same shadow-weighted algorithm from 1980 was used to adjust the NPDC curves in shadow areas to fit any printer’s dynamic range, while preserving crucial highlight tonality.

To standardize gray balance, we followed the logic of the ICC’s relative colorimetric rendering intent, defining CMY gray balance as a function of paper color, reduced in proportion to dot percentage. This also mimics the human visual system’s “chromatic adaptation” phenomenon, and a camera’s auto white balance function.

GRACoL2006 and its sister SWOP2006 color spaces were wildly successful but to our surprise, many people were more interested in the P2P calibration method, so I donated it to Idealliance who re-named it “G7”, and the rest is history.

CR:     You encountered a lot of resistance initially. Can you give us some insight as to what that was like?

DH:     A fundamental rule of science is that any new discovery should be challenged rigorously. And a fundamental law of human nature is to resist change for change’s sake. So it’s not surprising that some industry experts and associations with a vested interest in the old TVI calibration method did their best to kill G7.

The main opponents to G7 were FOGRA, ECI and BVDM – three German associations roughly equivalent to Idealliance, that do great work in promoting standardized printing in Europe.

In 2005 I offered the P2P system freely to FOGRA and ECI, and suggested they partner with Idealliance in its development. But the request went unanswered until January 2006, when they announced their PSO certification system, which had been developed in secret while G7 was an open, public project.

PSO is based rigidly on the ISO 12647-2 standard, with emphasis on TVI curves, while G7 exposes the weaknesses of TVI and provides a more effective alternative. G7 was obviously seen as a threat to the revenue potential of PSO, but the PSO program could easily have replaced TVI with G7, or offered the option of TVI or G7. Instead those organizations refused to acknowledge G7’s many benefits, and took instead an aggressive public stance against G7, Idealliance and myself personally.

The good news is that ten years later, G7 has been far more successful than PSO, largely because it works more effectively, is far less expensive and can be used on any printing system, not just offset. There are now hundreds of G7 Master sites and thousands more unregistered users world-wide. In fact many German and European printers and print buyers have secretly adopted G7 – they just don’t advertise it.

CR:     When did you know that G7 was going to become the de facto standard?

DH:     As soon as we released GRACoL2006, it became obvious that much of its appeal was in the G7 calibration process. In 2006, Idealliance provided the G7 How-To and GRACoL and SWOP profiles freely, with thousands of downloads in the first few weeks. Printers all over the world began praising G7 as the first really useful calibration system they’d ever tried, even if they weren’t printing to GRACoL. Other processes like Flexo, screen, xerography, gravure, etc. also adopted G7 because it made life easier – especially when they had to come as close as possible to a GRACoL proof without the benefit of ICC color management.

CR:     What are some misconceptions some folks might have about adjusting color through grays?

DH:     The most common misunderstanding about G7 is that it’s a replacement for ICC color management, which is not true. G7 uses just four one-dimensional curves to achieve good gray balance and tonality, much as a photograph’s exposure and color balance problems can be “corrected” in Photoshop with RGB curves alone. When grays are corrected, colors are moved in the right direction, but may fall short of complete accuracy depending on additional factors that cannot be corrected with simple 1-D curves, like ink hue, trapping and opacity.

By contrast, ICC color management uses more complex n-dimensional Look-Up Tables (LUTs) to apply hue, saturation and lightness changes discretely to different colors. G7 generally does a better job on neutral grays, however, and provides several additional benefits, so the best of both worlds is to use a combination of G7 plus ICC.

CR:     Is there any color device that cannot be brought to G7 standard?

DH:     No, but systems that don’t have user-programmable 1-D LUTs may not be compatible with the G7 calibration method. In those cases, ICC profiles can simulate a G7-based color space like GRACoL, with the same visual effect, but without the special benefits of separate G7 calibration.

CR:     Are there any particular books, white papers, YouTube channels or other reference sources you might recommend to color management beginners?

DH:     One of the earliest but still one of the best books on color management is Real-WorldColor Management by Fraser, Murphy and Bunting. For color geeks, I recommend Measuring Color by R. W. Hunt. The annual PIA Color conference (www.cmc.printing.org) is another excellent color management learning resource.

CR:     What are you working on now? How’s it going?

DH:     As a photographer, one of my life-long passions has been “expanded gamut” printing, i.e. getting more color out of conventional printing to make it look more like photography. My most recent efforts in that regard contributed to the new Idealliance XCMYK color space and methodology, which is based on maximizing the color gamut of four-color offset and can be simulated on any digital color system with sufficient gamut. In 2017 Idealliance will extend that work to consolidate and standardize both 4-color and 7-color expanded gamut strategies, ink sets and workflows.

CR:     I know you are a great lover of IPA’s. Got a favorite, and why?

DH:     America is blessed with the greatest selection of micro-breweries in the world. The beer I drink most often is Dale’s Pale Ale, whose red, white and blue can prevents oxidation by light. Dale’s has an excellent balance of hops without the excessive alcohol levels that spoil so many IPAs. Other good brews include Sierra Nevada, Anchor Steam, Lagunitas, Stone, and many others.

Many, many thanks to Don for taking time out of his busy schedule to speak with us.

To see and hear Don speak about the G7 protocols, as they apply to wide format printing, click HERE.

Check our Definitions page for many of the terms used above.

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Do you have a color management question, horror story or event to share?

Email me at reilley4color@gmail.com

Troubleshooting Color: Media Parameter Setup

More than once I have been asked: "OK, so the color is wrong, how do I make it right?"

Troubleshooting CMYK color can be a pain, because there are often many places the problem could be lurking, and changes made in one, may inadvertently alter the output based on info from another. So in this five part series, we will look at five important steps to troubleshooting a color managed system, or colorimetric tuning.

As you all know, a color management system is usually broken into five parts:

1. Source color space
2. Media parameter setup
3. Source color space designation
4. Output color profile
5. Output calibration set

Part 2 - Media Parameter Setup

There are many different kinds of paper, such as recycled and rag paper for newspapers, glossy coated paper for magazines, uncoated paper for stationary and bright-white coated paper for high-quality brochures. Some paper is coated for a particular ink, some has already been printed on (shells) and some is in fact black, or darkly opaque for printing on a 5th color station press, using white toner. And now synthetics have become a hot trend in digital printing.

As you can imagine, each type has different characteristics when it comes to printing. The recycled paper sucks up more ink, and if you don’t take this into account, your beautiful full-color photos will become too dark, and the ink will blur over the paper, creating an ugly brownish effect. Coated paper reflects light differently, and distinction between matte & gloss can make a LOT of difference to the final colors.

So, how do you optimize artwork for all of these different kinds of papers? Well, that’s the easy part. 

Standard CMYK inks have been tested on every type of paper imaginable. The way cyan, magenta, yellow and black are printed on a specific type of paper is documented in an ICC profile (a complete record of a print device's color gamut). All you need to do is download these free “Color Profiles” and select the right one when you export a PDF using InDesign (Export → Output → Color Conversion & Destination). 

In Photoshop you can use these profiles as input profiles, to soft-proof colors printed on specific stock.

To learn more about profiling, read Calibration and Profiling

The RIP's job parameters related to media setup and imaging style must be consistent for the customer’s job, as well as for the related profile generation and calibration pages. 

A specific determining factor is Fuser temperature: Higher fuser temperature results in increases in gloss and density.

The primary specification for fuser temperature is Paper Weight, with a lesser degree of control through paper type (Plain, Glossy, Matte). Fuser Nip (dwell) and direct Fuser Temperature setting in the paper catalog entry also have an effect on fuser temperature.

Halftone Mode: Also known as screening type. Specifies whether line or dot screening is used, and in
some print devices, the halftone resolution (lpi) and native resolution (600 or 1200).

Resolution: Effective pixel addressability, collected pixel size and gray tone possibilities. May be
specified combined with Halftone Mode.

These job properties must be decided upon prior to any further color tuning, and used for all customer
jobs, calibration sheets and profile targets for the applicable job/media setup. Of course, any given
machine and customer may use one or more job/media setup with varying parameters.

Any adjustments determined in Print Engine Setup should be applied via SP mode and/or a paper
catalog entry and used for all applicable prints.

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Do you have a color management question, horror story or event to share?

Email me at reilley4color@gmail.com