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

How Color Print Tricks the Eye

Consider for a moment the marvel that is color printing.

It uses a scientific trick of lightwaves - Metamerism - plus engineering marvels that electrostatically charge a piece of media in very specific places, then release precisely placed, incredibly small grains of colored toner, and a developer fluid that reacts with the fuser's heat to bond those particles, all to trick your eye into thinking that a reflective surface is an emitting surface.

Hundreds of times a minute.

Or spray micro-drops of ink from two directions at once as the media rolls by.

And the controlled combination of colored toners or inks trick our eyes into interpreting a reflective surface as if it were an emitting surface. This is a trick worthy of magic, but really, it's science.

Here is a basic explanation of the color spaces involved with printing.

Simply put, the Cyan, Magenta and Yellow printing inks cancel out the Red, Green & Blue wavelengths of light coming to our eyes from the media's surface, metamerizing the wavelengths, tricking our biological processor into thinking it is the RGB of our human color vision.

Why red, green and blue? You may remember from science lessons in school - visible light is a spectrum of light, described as frequencies, ranging from reds through the colors of the rainbow into blues and purples.

From a scientific point of view, light can be a mixture of any of those monochromes, light of a single frequency.

However, we have light-sensing cells called cones in the retina of our eyes to detect the amount of light in the red, green and blue areas of the spectrum. Because of this, “true” monochromatic yellow light, which lies between red and green on the spectrum, is indistinguishable from a mixture of monochromatic red and green light.

From a design point of view, since we can’t perceive the difference, it simply does not matter, and so we can abstract any color we can see as a mixture of red, green and blue.

The science of digital color, however, describes color using the L*a*b* color model, among others, which is a bit less intuitive but more closely approximates how the human visual system works.

It uses the Lightness values of an image (the grayscale version) as an axis to rotate opposing poles of chromacity described as a* (red vs green) and b* (yellow vs blue) to describe the gamut of human color vision.

“But wait," I hear you cry, “You just told us human eyes sense red, green and blue!” That is true, it’s called the Trichromatic model of vision, and while it describes how the individual cones in the eye work, it doesn’t accurately describe the visual system as a whole.

Separating the human perception of lightness from color leaves the a & b dimensions as measures of chromaticity, brightness independent of color. This is important, as some colors appear brighter or darker, despite being at the same intensity.

For instance, we see a fully saturated yellow as a lot brighter than a fully saturated blue.

Regarding ranges, L is measured from 0 (dark) to 100 (light), a from -120 (red) to +120 (green), and b from +120 (yellow) to -120 (blue).

So let's look at the rods and cones mentioned above.

Human color vision takes place in the retina, and ends deep in the brains 's visual pathways.

The ventral stream (purple) is important in color recognition. The dorsal stream (green) is also shown. They originate from a common source in the visual cortex.

The retina is the innermost of three tissue layers that make up the eye. The outermost layer, called the sclera, is what gives most of the eyeball its white color. The cornea is also a part of the outer layer.

The middle layer between the retina and sclera is called the choroid. The choroid contains blood vessels that supply the retina with nutrients and oxygen and remove its waste products.

Embedded in the retina are millions of light sensitive cells, which come in two main varieties: rods and cones.

Rods are used for monochrome vision in poor light, while cones are used for color and for the detection of fine detail. Cones are packed into a part of the retina directly behind the retina called the fovea, which is responsible for sharp central vision.

When light strikes either the rods or the cones of the retina, it's converted into an electric signal that is relayed to the brain via the optic nerve. The brain then translates the electrical signals into the images a person sees.

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

Email me at reilley4color@gmail.com

Metamerism

Things That Go Weird in the Light.

Have you ever compared two garments in a store and decided they matched, only to find that when you left the store and went out into daylight they no longer matched and instead looked quite different? Do you recall the blue & black / white & gold dress image that was an internet meme not long ago?

If so, you have seen an optical phenomenon called metamerism failure (muh TAM erizm). Strictly speaking, metamerism occurs when you see two samples match under one light source (illuminant) and not match under another.

How can this be?

Well, it comes down to the difference between how an object affects light, and the color it appears to our eyes. Objects affect light by selectively reflecting or absorbing light of different wavelengths. So an object that absorbs most blue wavelengths and reflects most red wavelengths will usually appear red to our eyes. The actual color it appears to us is dependent on the spectral composition of the light reflecting off the object.

Let's say, for example, we have two objects that each reflect red light in approximately the same way but one reflects blue light while the other absorbs it. If you put both objects under reddish lighting (and most indoor tungsten lighting falls into this range) then they may appear to be very close to the same color. As there is very little blue light falling on our objects, the difference between their blue reflectiveness is almost invisible. The red reflection is about the same so they both reflect similar wavelengths and our eyes see them as the same color!

This would not be a problem if we didn't have many different colors of lighting in everyday life.

So let's take our objects outside into mid-afternoon daylight. Sunlight at that time of day contains considerably more blue light than indoor lighting. As before, our pair of objects will reflect red light similarly but one of them will reflect a significant amount of blue light while the other absorbs it. Our eyes will see the blue light from one object combined with the red light and we would probably call the result magenta. Suddenly what we thought were two reddish objects no longer match at all!

In many ways this very phenomenon is essential to color reproduction, which we discuss below, but when colors "shift" from our expectations, clients stop paying bills, and that is a problem.

The fundamental reason for metamerism is that color is a sensation rather than a property of an object. As a result, the cones in your eyes can register the same sensation from an essentially infinite variety of combinations of different light frequencies.

Color perception basically requires four factors:

Light Source + Object + Observer + Interpreter = Perception.

Where will we see this problem in the business of digital imaging?

• Proofs and press jobs failing to match under different lighting.
• Color builds chosen for normal printing failing to match under unusual lighting. A good example of this is trade show booths and how they are lit with unusual lights in exhibit halls.
• Two prints using different technologies - such as inkjet vs photographic print - failing to match under certain lighting.
• A product shot failing to match the product in all lighting conditions.

Can color management using ICC profiles correct for this problem?

No... and yes. ICC profiles are typically built using readings referenced to D50 (5000K) lighting. That means that prints created using these profiles will look best under D50 lighting. Viewing them under any other lighting can give unpredictable results.

Most printing pigments and dyes have been carefully chosen to not conflict with each other or other pigment sets. One exception that is appearing more and more is pigmented inks for inkjet printers.

Sometimes you can measure printed or scan/camera targets with a different light source such as D65 in the calculations. This should make the print viewable optimally under D65 lighting. This is not always successful and requires the appropriate settings to be available both on the instrument and in the software.

Papers manufactured with optical brighteners are especially susceptible to color changes when lights differ in their short wavelength radiation, which can cause some papers to fluoresce.

One closely-related problem cropping up more and more often in the inkjet printing world is often (incorrectly) called metamerism.

When colorants are mixed carefully in a printer, you can achieve a smooth, neutral gray gradient from black to white. With most inkjet printers, the ink combination will include Cyan, Magenta, and Yellow inks in varying amounts along with Black ink. When properly balanced, pleasing black and white images can be printed. Many users are also experimenting with near-neutral imaging such as adding a slightly blue or sepia tone for effect.

With the fugitive nature of dye-based inks, many users are switching to pigment-based inks for the vastly improved permanence. After all, if you are printing and selling works for display, your customers tend to have the expectation that the work will last beyond 2-3 years. Pigmented inks however, can suffer from a pigment balance problem which rears its head in a similar manner to the two-sample metamerism problem.

It is important to note that this is not an expected color shift but rather a shift that appears strange to the eye.

One would expect that a gray tone viewed under D50 lighting would appear to be a warmer gray when viewed under warmer, tungsten lighting. The color balance failure we are referring to here shows up as a green or magenta cast and is noticeably different than a shift normally attributed to warmer or cooler light.

Many people incorrectly refer to this phenomenon as metamerism.

Metamerism, however, is specifically defined as a phenomenon that occurs between two samples. The ink balancing situation does not involve two samples but rather a balance of pigments in one sample.

Strictly speaking, then, it is not metamerism and the problem is more correctly referred to as Gray Balance Failure or Color Balance Failure.

After all is said and done, it is fair to say that metamerism is the enemy of digital printing, right?

Not really, no.

Metamerism, remember, is when an object matches another under a certain illuminant even though the spectral characteristics of the two objects differ. The act of balancing three or four colorants (such as CMYK inks) so they appear to be the same color as an original object is also based on metamerism.

Because of the 3-channel nature of our eyes, we can get 4 inks to appear to match a real-world object like a person's face without the spectral characteristics of the inks resembling the face much at all. This means that the print and the face affect light differently but appear to be the same color to our eyes!

This is the basis of digital imaging and printing today. It is fair to say, then, that without metamerism we would not be able to do ANY of the imaging we do today! It is only when the balance fails that we call it a problem.

Perhaps a match-failure problem should be called metamerism "failure" rather than metamerism, but this term does not seem to be used at all.

As with anything in the color management world, being aware of the problem is half the battle. Now that you know about metamerism and GBF you can consider it as a contributing factor when things don't look right.

Also, if you have no D50 lighting under which to view your prints it is possible they will never look quite right. Invest in controlled lighting for print viewing. With the many variables in digital color work that can give you problems, nailing down lighting is considered a basic requirement for print viewing as well as monitor to print matching.


Since it may be impossible to completely control the lighting conditions under which colored objects are stored, displayed, or judged, the best way to prevent metamerism is to match the object with pigments with exactly the same reflectance properties. In color matching, this precision is the goal of every colorist. However, sometimes their goal cannot be met because the pigments in a target sample submitted for matching may be inappropriate for the planned application.

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Do you have a color management question, horror story or event to share?
Email me at reilley4color@gmail.com