Wednesday, May 30, 2018

How well do we remember color?

In a previous (and highly entertaining) blog post, I reviewed two studies that tested people on brand color recognition. The studies were not peer-reviewed, Nobel prize winning efforts, but enough effort was put into them for me to find the results suggestive. I don't mean that in a salacious way; I do mean that the experiments suggest that our recognition of brand colors is not as good as we might think it is.

The sight of Starbucks periwinkle makes me thirsty

In today's post, I will take a dive into what peer reviewed Science has to say on the matter, specifically on the topic of how accurately we remember colors.

What I didn't study

There are a lot of stones in this field, and I left a lot of them unturned. Here are some exciting topics that I skipped over...

Color and emotion - This is a big field. It would be cool to really dig into how color effects us emotionally. I would love to separate the wheat from the chaff (valid research from pontification). The paper by Yu et al. Looks like it would be fascinating. But, I didn't really look at it for this blog post.

Color and emotion and brands - Another mondo interesting study would be to look at our emotional reaction to the color of a box of cornflakes. Presumably, there is an ideal corn flake box color that will seduce the unwary buyer into filling the shopping cart. Gosh, I would love to learn all about that. I bet the paper by Rupert et al. would be a great place to start.

Color constancy - There has been all this research around the cool topic of how it is that our perception of the color of something doesn't change all that much when the illumination changes drastically. Like from the yellowish incandescent light in your living room to the blueish light outside. There is a huge difference in the spectra of the light hitting your eye, but we still see white paper as still being white. This is the kinda topic that makes people want to quit their day job and become a PhD candidate! But I'm not going to talk about it. Well... maybe I will mention it in passing.

Many roads diverged in this multicolored wood, and I am sorry that I could not travel them all. I took the one less traveled. 

Color memory

Here's what I am thinking: I have a picture in my head about what Starbucks green is. I see it as a darker shade of green that might be just a tiny bit toward the blue end. But, my memory of Starbucks periwinkle is wrong. If you don't believe me, just ask my wife. She is the world's authority on all my shortcomings, and would love to acquaint you with my multifarious imperfections. But, everyone's memory of the official Starbucks green is not quite perfect. How far off are we?

I just can't remember the name of this film

We all know that a banana is yellow, and a school bus is a slightly orange flavor of yellow, and the color of an orange is slightly weaker than true orange, but that carrots are true orange, which is why we call them carrots. These are all memory colors.

Carrots should really be called oranges

The idea of memory colors dates back to Ewald Hering in 1878. Loyal readers will remember that Hering has been mentioned in a few of my previous blog posts. Hering is the guy who developed the color opponent theory. This theory says that we can assess any color in terms of three attributes: where it fits between white and black, where it fits between red and green, and where it fits between yellow and blue. This is how color is encoded on its way to the brain, and this idea was baked into CIELAB.

Hering's three attributes of color

Hering made another contribution to color science. He said that our perception of the color of an object is effected by our memory of the color of a prototypical object. Like, if we see a banana that is kinda yellow, but not quite, we will remember it as being yellow. Remember how I said that I was gonna mention color constancy? Now is the time. Hering's theory has been used to explain color constancy. If the yellow of a banana has a slightly unusual shade, then our brain will use that fact to deduce the color of the illumination.

There is a prediction from Hering's theory of color memory that is important for the purpose of this blog. If his theory is true, then our memory will tend to bias toward the quintessential version of that color. We will remember our bananas being yellower than they really are.

David Katz reiterates Hering's theory:

... in the imagination we exaggerate colours of objects whose colours are generally distinguished only in terms of brightness, darkness or hue. If we ask a person to pick out a blue which will match the colour of the eyes of someone he knows very well, he generally selects a blue which is too saturated. If we ask a person to match a brick, he usually chooses a black which is too deep or  reds which are too highly saturated. Almost always he selects a colour which is too bright to match a bright object, one which is too dark to match a dark object, and one which is too saturated to match an object which is known to have a distinct hue.


Katz liked Hering's theory on the distortion of colors by our memory

If this theory is true, then our color memory is flawed, so our recollection of Starbuck's green is flawed. The practical message for everyone in the business of making sure that Starbucks has the correct shade of green is that the exact color of the logo doesn't really matter, since we will identify the logo by it's shape, and our brain will translate the color into the correct shade of green.

Wow. Big stuff here.

What does the research say?

Hering was a brilliant guy, and rates up there with Munsell as one of the Fathers of Color Science. But he was largely a theoretical guy. Have experimental results backed up his theories of memory colors?

An early investigation by Adams provided evidence that agreed with Hering, but it was inconclusive. 

From our investigations of the perceptions of the five natural objects grass, snow, coal, gold and blood, we may say that Hering and Katz were correct in claiming that the seeing of these objects is ordinarily affected by memory color. Although our investigation failed to give a quantitative measure of a single memory color, it was thus not unfruitful.
Adams (1923)

Five memory colors from Adams' paper

Not unfruitful? I didn't see a single fruit in their list of memory colors! It is likely that the hard results were lacking because of the lack of rigor in this paper. To be honest, the paper reads like a cheap and boring novel with pages and pages of one anecdote after another, and then a short experiment.

Bartleson provided a more rigorous test of memory colors, using colors of ten familiar objects: red brick, green grass, dry grass, blue sky, flesh, tanned flesh, broad-leafed summer foliage, evergreen trees, inland soil, beach sand. Here is their assessment:

Each memory color tended to be more characteristic of the dominant chromatic attribute of the object in question; grass was more green, bricks more red, etc. In most cases, saturation and lightness increased in memory. 

There is evidence of increased saturation in the memory colors. In most cases there are hue shifts with memory in the direction of what is probably the most impressive chromatic attribute of the object in question.
Bartleson (1960)

The grass is always greener in our memory

A bit more recently, Siple et al. did a similar test with six foods (carrot, corn, lettuce, lime, orange, and peanut), and agreed with the theme that we remember colors as being more vivid. Note that their test was the first that was literally fruitful, since they included oranges and limes.

Results indicated that, for hue and brightness, memory and preference were quite accurate for the objects tested; however, all subjects remembered and also preferred all items to be more highly saturated.
Siple and Springer, 1983

One could argue that trying to recall the color of grass is a bit problematic. After all, the color of grass varies with species. Is it Kentucky bluegrass? Fescue? Rye grass? Easter grass? The color also varies with the plenitude of rain, nutrients, and sun. And where my doggies have visited.

Three recent papers (one by Bloj et al., one by Pentz, and the final by Newhall et al.) sought to eliminate this problem of variability of the colors of real objects. Bloj asked subjects to bring along a familiar object. Even when recalling those familiar and well-defined colors from memory, the conclusion of this paper was that "Our results, on average, confirm that objects are remembered as more saturated than they are."

Somehow Johnnie graduated from Kindergarten despite his sub-par drawing skills

On to Pentz's paper. He taught a color class for several years, and recruited the members of each class for an experiment, eventually testing 283 people. The people in the class were shown a blue piece of plastic and were told that they would need to recollect the color later on. They each had a chance to hold the plaque and could look at it as long as they wanted. Later, they were shown a collection of 24 plaques which included the one they had looked at. "Only thirty percent of participants at plastics coloring seminars were able to correctly identify a color observed only an hour earlier." While the correct plaque was determined by the most participants, the two next most likely guesses had a color difference of about 10 ΔE from the correct plaque.

(How big is 10 ΔE, you may ask? Imagine a color match that is as big as you might consider acceptable for production. Then multiply that by 2 or 3.)

Newhall et al. looked at our short term memory of colors in order to eliminate the ambiguity for familiar objects. The subject was shown a color for 5 seconds, given a 5 second break, and then asked to adjust knobs to recreate that color. Here is one of the conclusions from the paper:

Significantly more purity and somewhat more luminance were required to complete the color matches by memory than were necessary for the simultaneous matches. This principal result was confirmed by the results of three supplementary experiments.
Newhall, Burnham, and Clark (1957)

Newhall et al. found that we remember colors as being higher in chroma (by 1.7 steps in Munsell chroma) and somewhat lighter. They also found no consistent change in hue between what we remember and what we see.

The typical migration pattern of a color trapped in a brain

How big is a step in chroma of 1.7? The data is all in the paper. I could type it all into a spreadsheet, convert it into CIELAB, and then compute color differences. But I could just be lazy and wave my hands. Fully saturated colors go up to maybe 15 in Munsell chroma, and maybe 100 in CIELAB C*. A step of 1.7 in chroma is roughly 10 ΔE. I dunno. I think this is kinda big for a 5 second delay.

One common theme from these experiments is that colors are remembered more vividly than they actually are. Whether or not colors are lighter in our memory and whether there is a systematic error in the hue are both up for debate.

Colligation

The ancient Greek, Ptolemy, developed a set of equations that could be used to predict the positions of the planets at any time. The equations were based on a lot of wrong assumptions, like "the Earth is in the center, and all the rest of the celestial bodies move in circles that revolve around other circles". The model worked, at least to an extent.

A millennium or so later, Copernicus decided that the Sun belonged at the center. Then Kepler came along and decided that ellipses made the whole thing simpler than the circles in circles thing, and then Newton provided the big colligation. The inverse square law of gravity was the grand unifying theory that explained the whole enchilada. If the pull of gravity goes in inverse proportion to the square of the distance between the objects, then planets will travel in Kepler's ellipses. Eureka!

By the way, colligation means "to subsume (isolated facts) under a general concept". I really love that word. It explains the essence of what I think it is to do Science: to find simple theories that explain lots of data.

We are ready for a colligation of our understanding of color memory. We have all this data from these studies. We have a generalization of how saturation changes when it gets implanted into our memory. It's a bit fuzzy what happens with hue and lightness, since the data doesn't always agree. We need an explanation that can tie it all together and explain some of the anomalies.

In this case, the colligation was fairly recent, by Bae et al. in 2015. The idea is pretty simple. We have a limited number of folders in the filing cabinet in our head. Although we can distinguish perhaps millions of colors, there are eleven basic folders where we store colors, at least in the English speaking world. The folders are labeled white, black, gray, red, orange, yellow, green, blue, pink, brown, and purple. This was the result from Berlin and Kay, and also in the groundbreaking experiment that I never got around to publishing.


Here is the grand and glorious theory of color memory distortion.....

When we want to store the color of an object in our brain, the first step is to categorize it into one of perhaps eleven archetypal colors. From there, presumably, we may make modifications to distinguish from the archetypal color (yellowish green, or dark red), and the modifications get stored along with the general category. Later when we retrieve that color from our memory, the archetypal color gets weighted a bit more than the modifier.

Evidence from Bae

Bae et al. had the participants try to remember 180 colors, equally spaced in hue, all with L* = 70 (fairly light) and C* = 38 (somewhat saturated). They saw the color for 100 msec, the color was removed for 900 ms, and then they had a chance to select the color from a ring.

The results of the paper are summarized in my drawing below. There are seven regions. Within any of the regions, for example, the blue one, people will tend to distort the hue toward the solid line which represents the archetypal example of that hue. (Four of the eleven basic colors were left out. White, black, and gray don't have a place on the hue circle. And since their L* was fairly high, they missed out on brown. They almost missed red.)

Hieroglyph found in a Mayan tomb, hitherto-for undecipherable 

This explains why the hue of a color sometimes shifted in the experiments, and sometimes not. But the color memory experiments seem to all agree on one thing. Our memory of a color is generally more saturated than the actual color. How does the eleven-folder theory of color memory explain this?

Here is a quote from Heider that can explain this:

It was quite clear, without further analysis, that the most saturated colors were the best examples of basic color names both for English speakers and for speakers of the other 10 languages represented.

When we think red, we don't think some wimpy-butt red. We think fire-engine-lipstick-Corvette-candy-apple-OMG-I'm-bleeding red. It only makes sense that most of the colors that were tested in the experiments cited above would not be the most saturated colors imaginable. Hence, our memory would tend to distort most of the colors in the experiments toward the extreme of saturation.

There are some archetypal colors that don't fit Heider's hypothesis, namely brown, gray, and pink. I would take a wild guess that these are the exceptions to the rule in the previously described experiments.

Why eleven?

Bae's research suggests that the eleven basic color names are the appropriate number. Or rather, it does not suggest that there are colors beyond the seven which qualify to be archetypal colors. But Bae's experiment, awesome as it was, only looked at 180 colors - all of which had the same L* and C*. There is quite a bit of uncharted color space.

Based on my personal experience, I would like to think that I have more than just eleven archetypal colors. I mean, I see tan, coral, olive green, and plum as distinct colors in their own right.

My candidates for induction into the Hall of Archetypal Colors

In some languages, such as Russian, Japanese, and Italian, there is a separate word for light blue which stands on it's own as a distinct color. So, maybe there are twelve archetypal colors? Dimitris Mylonas (Mylonas and MacDonald, 2015) suggested that lilac and turquoise also belong on the list. In two other papers, he has named a much larger collection, including cream, lime, olive, salmon, mustard, peach, tan, and coral.

So, I don't think we can say at this time that there are exactly eleven colors that serve as archetypal colors in our memory. There could be more. It also seems quite plausible (to me) that the number is different for different people. I would think that people who deal with colors all the time (like artists, graphic designers, fashion designers, interior decorators, and the spouses of color scientists) might have developed a wider collection of focal point colors. On the other hand, it could be that the relatively small collection of focal point colors are a result of something hardwired in the brain.

Here's another interesting thought. We know that some people have perfect pitch, an uncanny knack to identify musical notes. All of these studies looked at people's color memory in the aggregate. Perhaps there were a few individuals whose superpower is to have perfect hue? I have heard more than one person make that claim. Of course, one person who made that claim also told me that he was raised from infancy by a troop of iguanas in a volcanic crater. He probably learned it from them.

All interesting stuff for further research!

Non-References

Burnham, Robert W., and Joyce Clark, A Color Memory Test, Journal of the Optical Society of America, Vol 44, No 8, Aug 1954

Rupert, Andrew Hurley, Rachel Randall, Liam O'Hara, Charles Tonkin, Julie C. Rice, Color harmonies in packaging, Color Research & Application, Volume 42, Issue 1, 28 March 2016

Yu, Luwen, Stephen Westland, Zhenhong Li, Qianqian Pan, Meong Jin Shin, Seahwa Won, The role of individual colour preferences in consumer purchase decisions, Color Research & Application, Volume 43, Issue 2, 10 October 2017

References

Adams, Grace Kinckle, An Experimental Study of Memory Color and Related Phenomena, The American Journal of Psychology, Vol. 34, No. 3 (Jul., 1923), pp. 359-407

Bae, Gi-Yuel, Maria Olkkonen, Sarah R. Allred, and Jonathan I. Flombaum, Why Some Colors Appear More Memorable Than Others: A Model Combining Categories and Particulars in Color Working Memory, Journal of Experimental Psychology: General, 2015, Vol. 144, No. 4, 744–763

Bartleson, C. J., Memory Colors of Familiar Objects, Journal of the Optical Society of America, Vol 50, No 1, Jan 1960

Berlin, B., and P. Kay, Basic color terms: their universality and evolution (Stanford, Calif.: Center for the Study of Language and Information 1969).

Katz, David, The World of Colour, Kegan, Paul, Trench, Tubner, 1935, p. 164

Heider, Eleanor Rosch, Universals in color naming and memory, Journal of Experimental Psychology, 1972, Vol. 93, No. 1, 10-20

Hering, Ewald, Outlines of a theory of light sense, Grundzüge der Lehre vom Lichtsinn 1905, translated 1964, Harvard University Press

Mylonas, Dimitris and Lindsay MacDonald, Online Colour Naming Experiment Using Munsell Samples, European Conference on Colour in Graphics, Imaging, and Vision - CGIV, June 2010

Mylonas, Dimitris, Mathew Pruver, Mehrnoosh Sadrzadeh, Lindsay MacDonald, and Lewis Griffin, The Use of English Colour Terms in Big Data, May 2015, AIC Midterm 2015

Mylonas, Dimitris and Lindsay MacDonald, Augmenting Basic Colour Terms in English, Color Research and Application, Volume41, Issue 1, February 2016

Newhall, S, M., R. W. Burnham, and Joyce R. Clark, Comparison of Successive with Simultaneous Color Matching, JOSA 47, No. 1, Jan 1957

Pentz, Anthony J., Does color memory exist?, SPE/ANTEC 1999 Proceedings (Society of Plastics Engineers Annual Technical Conference and Exhibit)

Siple, Patricia, and Robert Springer, Memory and preference for the colors of objects, Perception & Psychophysics, 1983,34 (4), 363-370

Thursday, May 17, 2018

Do you remember a logo?

I stumbled across a quote the other day that I found interesting. This was on the Coca-Cola website:

"There is no Pantone color for Coca-Cola red, but when you see it, you know it."

Ah! To be tanning under the Coke Red Sun!

This sounds like one of those factoids that everyone knows is true, so nobody would be crazy enough to actually test it. Well, guess what? I know a few crazy people. In fact, one of my best friends, Eddy Hagen, has recently tested this very thing with an online test: how well can you pick out Coke red?

(As an aside, here is the process for joining the John the Math Guy's Best Friend Club: Connect with me on social media. Contact me somehow or other with a message that does not contain the phrase "John the Math Guy is a doofus." Then you're in. If you just want to get on my email list, then send an email to john@johnthemathguy.com to subscribe.)

There are two tests in Eddy's blog. In the first test, Eddy tests your short-term color memory . You are shown a color, and then asked to pick it out of a line-up later. That one is kind of a warm-up to the real test. In the second test, he shows you a bunch of colors and asks you to pick out Coke red.

Do people know Coke red when they see it, as the Coca-Cole website suggests? He shares the results in another blog post. I don't wanna give anything away, but the title of this post is You can’t correctly remember an iconic color, not even Coca-Cola red.

Which one makes you thirsty?

Who is right??!?!? Let's get to the bottom of this!

Brand color is important

Brand colors are important, especially if you have a brand to sell. Here is what Axel Kling (Print Quality Assurance Manager for Coke) has to say about the importance of brand colors:

In today’s marketplace of unlimited beverage choices, a brand’s first point of contact is most likely to be at the point of purchase. And how well your product stands out on shelf could determine whether it’s put in the shopping cart or left behind.

I know most of my readers have private chefs who do their grocery shopping, but imagine if you will, being in the snack aisle of a grocery. You are trying to find your favorite bran cereal with raisins. Just reading that line, I'm gonna guess that you're thinking "purple". Am I right??! Of course, the image below wasn't any clue.

When I am old, I shall eat cereal out of purple boxes

The bran owners of the various raisin brands have trained their cereal boxes to be distinctive colors so that they can jump off the shelf into your shopping cart. And lets, face it. Nothing says "raisin bran demographic" quite like the color purple.

This is an aside, but how can Kellog's and Post and Trader Joe's and Total and John the Math Guy Breakfast Foods all use the name Raisin Bran? Interesting trademark factoid: The Skinner Manufacturing Company was the first to sell raisin bran, back in 1926. It trademarked the name, but in 1944, the Supreme Court rescinded the trademark, saying that you can't trademark a simple description of a product.

Speaking of trademarks, the color purple, and brand colors ... In 2004 Cadbury applied for a British trademark for the color purple (Pantone 2685C)  "applied to the whole visible surface, or being the predominant colour applied to the whole visible surface, of the packaging of the goods." Nestle objected, and their application was denied. It seems you kinda have to have a mark, if you want to have it trademarked. But, this trademark application in 2004 was a revision of an earlier trademark from 1995, which is still in force, at least until Nestle contests that trademark. 

Imagine my surprise when I found out that the chocolate wasn't purple!

This is in the UK. I apologize in advance to my British friends and enemies, but I'm not all that excited about British law. I mean, back in 1492, we fought the Spanish-American war to get away from having to follow your laws about tacks in our tea. What about US trademark law and colors?

I read up a bit on Wikipedia about color trademarks. In the US, you can trademark a color so long as it serves no other purpose other than to distinguish your product. So, Johnson & Johnson can trademark the name Band Aid, but not the color, since that serves as camouflage on certain people's skin.

There are a number of colors that are trademarked in the US, as shown in the image below. I compiled these from the Wikipedia article and the Business Insider article Can You Identify These 12 Brands By Their Trademarked Colors Alone?


I am gonna conclude that at the very least, brand owners think that brand colors are important.

It's not just about being able to find your favorite cereal

Color is about brand recognition, It helps you find a specific product within a dazzling array of colors. But the prevailing wisdom is that it also communicates something about a product. Red universally means romance or hookers, except when it's used on a fire truck or a stop sign. And of course, it doesn't mean romance if you are in China, where red signifies joy and luck. Or on one of my earlier blog posts where I decided it just signifies excitement, which explains why double-decker buses are red. But trust me. The meaning of a color is universal and unambiguous.

John spent the better part of an afternoon looking for his cereal

I have heard several presentations at conferences where the speaker says something like "color accounts for 86.3% of our buying decisions". As a math guy, I know that 95.4% of all statistics are made up, so, is there any definitive research behind the importance of brand color? Or is this just one of those statistics that gets quoted enough so that it becomes established fact?

Here is a quote from Daivata Patil that sounds authoritative:

Color is ubiquitous and is a source of information. People make up their minds within 90 seconds of their initial interactions with either people or products. About 62‐90 percent of the assessment is based on colors alone. 

Authoritative, with numbers and everything. But the article does not describe how these numbers were determined or even give a reference to where they came from. Hmmm.... urban legend?

Here is a similar quote from Axel's presentation. Remember Axel? The color guy with Coke? He attributes this quote to Jill Morton's Color Matters website. Both attribute it to Loyola University.

Color increases brand recognition by up to 80%. 

I googled this quote to try to find a link to the actual study. Note that I put quotes around the words so that Google knew that I was looking for those exact words in that order. Goggle told me there were "About 2,170,000 results"! I admit to not reading through them all. I looked at the first ten hits, trying to find the title or author of the study, or maybe a link. All of them mention Loyola, and several of the web pages reference Jill Morton. None of them give any more information about the study.

Time for an infamous John the Math Guy tirade. This is not Science. I'm not saying that I have reason to doubt the statement, or that the various places that provide this quote are required to track down and report the original source. It's just that, for me, I would like to assess the strength of the argument. Was this an undergrad student who made up the numbers the night before the term paper was due? A professor who assembled twenty students for a little test? Or was this a master's thesis with hundreds of volunteers following a rigid experimental protocol?

Gregory Ciotti expresses my concern a bit more emphatically than wishy-washy me:

Most of today's conversations on colors and persuasion consist of hunches, anecdotal evidence and advertisers blowing smoke about "colors and the mind."

Getting back to the topic

Let me take a minute to try to remember where I was going with all of this. Oh yeah. Eddy Hagen's experiment about Coke red recognition.

Eddy's online experiment carefully explains the methodology and the results. It's Science, but I'm not gonna claim that Eddy's online experiment is good solid Science, and I don't think Eddy would either. He acknowledges that not all monitors are calibrated, and surveys where the participants are self-selected are a bit less rigorous that random selection. It could be that zealous PepsiCo employees deliberately failed the test to discredit their competitor. Or it could be that some of the individuals clicked at random just cuz it was late at night and they were waiting for the pizza guy to arrive.

Signs.com did another test of people's ability to recall brand logos. They brought in 156 people, and had them draw the logos of ten well-known companies from memory. This involved recalling not only color, but the shape and text of the logo.

Can you draw these from memory?

They have some stats on various aspects of the logos, but I did my own counting. I looking only at whether they got all the right colors, without adding extraneous ones. The results below are not all that fabulous, especially for multi-colored logos.

Company
Correct
Colors
7-Eleven
14%
Green, Orange, Red
Burger King
20%
Blue, Orange, Red
Foot Locker
38%
Black, Red
Walmart
49%
Blue, Yellow
Dominos
53%
Blue, Red
Starbucks
53%
Green
Ikea
56%
Blue, Yellow
Apple
72%
Black
Target
84%
Red
Adidas
92%
Black

I will point out that I was rather lenient about allowing different shades of the correct color. I allowed an orange flavored yellow to count as a yellow, or for Ikea blue to be too light or too dark. The image below shows the variation in color for Satyrbucks, which uses only green in the logo.

156 guesses at Starbucks green

At the far left, you see all 156 logos as drawn by the participants in the survey. (You can see a full sized version of this on Signs.com website.) In the middle drawing, I pulled all of the green pixels from each drawing, and averaged them together to show the green that the participant chose. At the far right, I show the 21 contestants that came within 10 DE2000 of the true Starbucks green. For reference, a common tolerance for commercial printing a color is 3.0 DE2000. Only two people out of the 156 participants were able to create a color from memory that would have been deemed acceptable printing of that logo.

Caveats...

I have made the assumption that there was an unbroken chain of proper color management throughout this process. If I had to put money on that, I would say that I would prefer to not put money on that. I don't say that to disparage Signs.com at all. I just know that the bar for rigor in Science is pretty high. But, looking at the middle image above... I rather doubt that any deficiencies in the rigor of this test could have caused that much variation in color.

Another caveat is in the interpretation of the results. This is a test of the participant's ability to recall the proper color from memory (as in Eddy's Coke red test), but also a test of the participant's ability to reproduce that color using the software provided. So, the logo drawing test is harder than the task of trying to find your favorite raisin bran.

Pondering

Eddy provided me with an interesting anecdote: "To put that unique Coke red in perspective: in the LinkedIn ‘Printing Production Professionals’ one of the printers that works for Coca-Cola shared that in the X-mas edition, the Coke red is slightly darker… (which I checked in my collection of Coke cans and it is correct) So if color is soooooo important, how does this different Coke red impact sales?"

I'm still kinda pondering why Eddy has a Coke can collection... but these two experiments beg the question about how precisely a brand color needs to be defined. Both experiments are well above the level of urban legend expressed by the statement "Color increases brand recognition by up to 80%". But neither experiment quite fulfills the high bar of rigor required to be accepted as peer-reviewed Science with a capital S. I don't expect to see either in the next edition of Color Research and Application.

But, the two experiments are suggestive, and that suggestion is a contradiction between the brand owner's expectations of what is needed and the psycho-physics of the color that we see.

In the next installment in this series, I will take a closer look at the Science that has been done, especially the Science having to do with our memory of colors. If you want a bit of a foretaste, look through the references below. I am going to pretend to have digested them in the next blog post.

References

Bae, G. L., M. Olkkonen, S. Allred, and J. Flombaum, Why some colors appear more memorable than others: A model combining categories and particulars in color working memory, J Exp Psychol Gen. 2015 Aug;144(4):744-63

Belcher, Teri, and Kevin Harvey, The Influence of Color, ANTEC 2007

Bartleson, C. J., Memory Colors of Familiar Objects, Journal of the Optical Society of America, Vol 50, No 1, Jan 1960

Burnham, Robert W., and Joyce Clark, A Color Memory Test, Journal of the Optical Society of America, Vol 44, No 8, Aug 1954

Ciotti, Gregory, The Psychology of Color in Marketing and Branding
https://www.entrepreneur.com/article/233843

Cunningham, Meagan, The Value of Color Research in Brand Strategy, Open Journal of Social Sciences, 2017, 5, 186-196

Elliot, Andrew J., Color and psychological functioning: a review of theoretical and empirical work, Frontiers in Psychology, April 2015, Vol 6, Article 368

Goguen, Kate, The Influence of color on purchasing decisions related to product design, Master's Thesis, Rochester Institute of Technology, Feb 20, 2012

Javed, Saad Ahmed and Sara Javed, The impact of product’s packaging color on customers’ buying preferences under time pressure, Marketing and Branding Research 2(2015) 4-14

Kling, Axel, The Importance of Color Management for a Consumer Product Company, Printing Industries of America Color Management Conference, 2011

Patil, Daivata, Coloring consumer`s psychology using different shades the role of perception of colors by consumers in consumer decision making process: a micro study of select departmental stores in Mumbai city, India, Journal of Business and Retail Management Research (JBRMR) Vol 7 Issue 1 October 2012

Mohebbi, Behzad, The art of packaging: An investigation into the role of color in packaging, marketing, and branding, International Journal of Organizational Leadership 3(2014) 92-102

Morton, Jill, Color & Branding, Color Matters
https://www.colormatters.com/component/content/article/62-color-a-marketing/240-color-a-branding

Satyendra Singh, Impact of color on marketing, Management Decision, 2006, Vol. 44 Issue: 6, pp.783-789

Tuesday, May 8, 2018

The heyday of expanded gamut printing patents

In the previous installment of this series on the history of expanded gamut printing, I chronicled three times where augmenting CMYK with a few extra colors was independently invented. There was such an uproar to my post that I had to write an addendum to add all the examples that I had missed.

At Hallmark Cards, the technique served a niche need for that time and place. The work of Harald Kueppers seems to have found a different niche, and gained some attention, but it saw limited use. And the developments at Dainippon, while they were very similar to what we see today, have left little trace in the history books. All the examples cited by friends also wound up being niches.

Sad fact: expanded gamut did not go mainstream during this time period.

One of the commentators on my post commented a comment about the futility of doing patent searches to dig up history. So today, I look exclusively at the patent record. In this blog post, I look at a period of twelve months in 1994 and 1995. These 372 days rocked the world of CMYK printing to its the very foundations. You think I'm being overly melodramatic? Consider this: These 372 days saw not one, not two, not three, four, or five, not six, but seven filings for patents on expanded gamut printing. CMYK printing. World of CMYK printing, consider yourself rocked.

Expand my expanded gamut, baby!

Hutcheson, Du Pont, March 29, 1994

If one cyan print unit is good, then two must be better, right? And if you print with two cyan print units, why not two magenta, and two yellow, and two black? The idea is to give a double bump anywhere that you need more ink than a single print unit can provide. This was invented by the very modest Don Hutcheson, and marketed by Dupont under the name HyperColor. I guess someone vetoed the name HyperDon.

Don'cha just love the cute drawings in patents?

The technique can be considered an expanded gamut process, since it does expand the gamut. It just uses CMYK as the additional colors, instead of OGV or some other collection.

Some of my readers may have met Don Hutcheson. He is still in the business, and is actually still working on this project. Idealliance's XCMYK project is a way to expand the gamut by pushing the standard CMYK to higher densities. After 24 years, one would hope that he will be making some progress soon.

A note on patents: Patents generally have a section at the beginning that describes the background of the invention or alternately, the prior art, that is, the existing stuff related to the new stuff being invented. The title prior art is actually shorthand for prior art bashing, since this section usually highlights the deficiencies of what is already out there. The prior art section is followed by an obligatory section  where the inventor explicitly states the purpose of the invention. This section is obligatory because patents have to be for something useful. I found that out the hard way when I tried to patent a wind tunnel with left-handed ear flaps!

What was the purpose for this (I mean Don's) invention? A quote from the patent: "... it is believed to be advantageous to provide a method for extending the color printing density range of a printing device without introducing special or non-process printing inks or unconventional pre-press proofing systems..."

Plettinck and Van de Capelle, Barco, April 29, 1994

Technically, this is not a printing method. It is a way to convert one color separation (based on CMYK) into another separation based on non-standard inks. What do they mean by "non-standard"? Here is an example from the patent:

For example, a chocolate manufacturer will prefer an ink set wherein brown ink plays a more dominant part.... So for example PANTONE (registered trademark) red, process yellow, and PANTONE brown form a set of non-standard inks that are used for printing packaging material for chocolate.

Reading the patent makes my mouth water!

Well... ok... maybe this isn't really expanding the gamut, although it could. I just couldn't pass up a patent that talked about chocolate. Those of you who are chocolate fanatics will understand.

What is the purpose of this invention? "The object of the invention is to provide a method for generating printing data wherein the second colour separation is determined in a more efficient and non-empirical way and a result is that the printing quality remains unchanged or is even increased."

Eder and Maerz, Eder Repros Offset Repro GMBH, May 19, 1994

This patent is in German, so I admit to not having read it in full. Well, actually, I didn't read any of it. But, I can tell you that Eder has been described by Anastasios Politis as: "One  of  the  most  significant  pioneers  in  processing  CMYK  +  x  colors...". I also know that Linotype-Hell marketed the Eder software under the name Eder MCS (Multi-Color Separation). More on that in a bit...

The company Eder still exists, and is doing software under the byline "product communication in the digital age".

Printing of the King Eider duck may benefit from ederMCS color separation

What was the purpose of the invention? I did some OCR on images from the pdf of the patent, and translated the German text into English: "It is therefore an object of the invention to provide a method for creating a color print image, with the help of which create high-brilliance color images, the required printing effort is reduced compared to the seven-color printing."

What is the purpose of me asking that question all the time? Please be patient. I am actually going somewhere with this. Suffice it to say that, so far, making prettier pictures has been the main goal so far.

Boll and Gregory, Eastman Kodak, October 21, 1994

One of the many things I like about writing patents is that the patent writer is allowed to be his or her own lexicographer. That means they can make up words! The title of this patent contains the word extra-quarternary, which I take to mean "beyond four".

Some comments on this uber-cool word. First, Harold Boll told me in an email: "I longingly love that word too, mainly because it should have been in the title of my first patent!" In the body of his patent, he used the word extra-quaternary. Due to a clerical error, an r was added to the word: extra-quarternary

Yoko was an extra-quaternary

Second comment on the word: several writers have used the term extra-trinary to connote expanded gamut printing. This is just plain wrong!

Kodak first got their feet wet working on a profile for Pantone's expanded gamut product, Hexachrome. More on Hexachrome later... 

Kodak had at least one major customer for their software product, Hallmark Cards. If you remember all the way back to the first blog post in this series, you will recall that Hallmark was big into expanding their gamut in the 60's.

I'm getting ahead of myself a bit here, but Kodak introduced an expanded gamut product called Spotless in 2011, 17 years after the Boll and Gregory patent. It is likely that there is not direct connection between the work of Harold and Spotless. Why would Kodak jump back into the expanded gamut ballpark? Hang onto that thought. I will come back to it.

What was the purpose of this invention? "It is another object of the present invention that it is uniquely capable of exploiting all of the attainable color gamut afforded by an n-ink (n>4) printing process and thereby achieves maximum colorfulness for rendered colors."

Maximum colorfulness... yum.

Herbert and DiBernardo, Pantone, November 29, 1994

Everyone in the print industry knows of Pantone. Lawrence Herbert is the guy who started Pantone. His son, Richard Herbert, took over the reigns. Lawrence and Al DiBernardo are the guys who invented Hexchrome, which was perhaps the most well-known of the mid 1990s commercial offerings for expanded gamut printing.

This system uses orange and green as the additional colors (there is no additional blue or violet ink). They wanted to keep the number of inks down to six, so as to make it usable on more presses. The ink set also includes richer CMYK inks, and some of the inks are fluorescent so as to make them more vibrant.

One of the things that distinguished Hexachrome is that they had a special fandeck for the Hexachrome colors. These guides had all the colors in their regular book, but with one difference. The regular Pantone guides have a recipe for how to mix each color in a bucket of ink. The Hexchrome guides have a recipe for how to mix halftones on press to make the color.

 Still available on ebay

If the fan deck of expanded gamut colors came from any other company, I would say that this was a brilliant marketing move. It certainly raised the awareness of the product to have a physical sample of the system. But since Pantone was kinda in the business of making fan decks, it wasn't so much brilliant as it was obvious.

What is the purpose of this invention? The first few words of the summary are: "A printing system for high fidelity printing of an image is provided..." 

According to the patent, Hexachrome is all abut making high fidelity colors. But (important point here for my narrative) the Hexachrome book really can't be used to make pictures.  

Seinfeld's 100th episode, February 2, 1995

The 100th episode of Seinfeld aired during the 372 days that rocked the world of CMYK printing. Coincidence?

Jerry Seinfeld has yet to comment
on his alleged links to expanded gamut printing 

Cooper, Linotype-Hell, March 27, 1995

This patent is a two-step process. First the CMYK separation is created, and then a correction is determined. This is all pretty obvious when looking at the diagram below from the patent.

The patent office desperately needs a service for
colorizing gorgeous drawing from old patents

Linotype-Hell released this as HiFi Color 3000 in 1994. In 1995, they announced that they would be selling the ederMCS package. It would have been interesting to have been a fly on the wall for the discussions they had about switching over to someone else's product.

What is the purpose for this invention?  I will skip the patent, and go to a press release for High Fidelity Color Printing:

Why would anyone want to print seven inks?
    • Seven inks can print a larger color gamut which includes colors that the four process color inks cannot achieve.
    • Seven inks can achieve a brighter color appearance and improved modulation of color.
    • Seven inks allow closer color matches to the original.
    • Printing with seven inks produces cleaner reds, greens, and blues.

Here is an interesting quote from the patent: "Spot colors are not considered in this application." Hang onto that thought. I will get back to it. Really. I am getting to something.

Bernasconi, Opaltone, April 5, 1995

Mathew Bernasconi developed a system of expanded gamut which uses CMYK+RGB. This is one of the few systems patented in the heyday of expanded gamut printing patents that has survived. This patent covers a device which scans a photograph and determines a set of color separations. Conceptually, there are two scans. The first scan is that of a traditional scanner, where a CMYK separation is done. The second scan creates a separation for the expanded inks to make up for the limitations of the first separation.

One difference between this patent and the others is that the extra-quaternary colors are preferably red, green, and blue instead of orange, green, and violet. Bernasconi explains the use of red over orange,

Orange is not a primary color, it’s a secondary (i.e mixed from red & green light). Therefore using orange ink in an expanded system actually restricts the color gamut. A red primary mixed with a yellow primary creates pure orange (see overprint image below) thus expanding the gamut whereby the red primary is also mixed with magenta to create “scarlet” reds. The hue angle difference between 100% overprint (R+Y) & (R+M) should be >30º. This hue angle difference cannot be achieved with 100%  (O+Y) & (O+M) because the orange is too yellow from the outset.

This is not the NBC peacock

Just in case you are getting a bit confused about which set of colors are being used as primaries, I provide the comparison in the image below. Which one is correct? The concept of primaries is based on RGB color theory, which is a simplification of color science. So, primaries are not really defined in color science. If, however, you seek your primaries based on color engineering, then the correct primaries are whatever set of pigments give you the biggest gamut. Finally, if you are a color practitioner, then the correct primaries are the ones that get you the colors that you want.

Comparison of the chosen ink sets

Another note on patents in general: the body of any patent describes specific embodiments of the invention. In the case of Bernasconi's patent, the addition of red, green, and blue inks to CMY is an embodiment. But the teeth of a patent is in the claims. The claims are generally much broader, covering many different embodiments. In this case, the first claim refers to "a plurality of data channels", instead of listing a specific set of inks. This means that the Opaltone patent could cover CMY+RGB (the preferred embodiment), or it could cover CMYK+OGV or RGB+CMYK.

In a much later patent (2011), Bernasconi described a CMY+RGB variation on this invention. Instead of using black ink, this system mixes red, green, and blue inks to make black. In this way, expanded gamut printing can be done on a six color press.

What was the purpose for this invention? "... saturated colours such as deep reds, greens and blues cannot be reproduced satisfactorily due to the limited print range of four colour process."

One more expanded gamut effort

Mark Mazur acquainted me with another expanded gamut effort in this time frame. He says that it was the first product in the packaging industry that allowed the user to select his own set of pigments.

The company is called Specialcolor. According to their website, they started selling expanded gamut color separation software (under the name ICISS) in November of 1995. This is just after the 373 days that shook the very foundations of the CMYK world, but I would argue that, had Glynn Hartley decided to file a patent, it would have been in the critical time period.

I did search for patents from Glynn. Couldn't find any in the US or the European database. His website doesn't list any patents, so I am guessing he never filed. That's not to say that he didn't invent anything that was patentable. I think it's a pretty good bet that there was something is this effort that would be inventive enough to get a few claims in a patent.

So what happened?

In 1991, Don Carli made a bold prediction "High Fidelity methodologies ... Represent a revenue opportunity potentially accounting for as much as 15 - 20% of the $150 billion dollar world-wide color printing market by the end of the decade." Speaking of cool made-up words, I should mention that Don Carli coined the phrase HiFi printing. I also remember hearing him refer to stochastic screening as sarcastic screening. Love the guy.

These predictions were enabled by technology in the mid 1990s. Back in the old days, the thing that made plates was a combination scanner (to scan the films), computer (digital or analog, to do the math for color conversion and screening, and platesetter (to make the physical plates). This is a pretty closed system. Only a few engineers really got a chance to play with the cool stuff inside. This changed in the early 1990s.

Apple provided affordable workstations that could play with images before they went to plate -- desktop publishing. In 1994, Creo introduced the first Computer To Plate (CTP) system. With these two pieces, a larger group of engineers could play with the way color is separated, and then make plates.

Gary Field points to another necessary technology that enabled the Heyday of Expanded Gamut Printing Patents: stochastic screening, AKA FM screening. When additional inks are added to CMYK, moire patterns show up. Icky, objectionable moire patterns. FM screening is a way to avoid these icky, objectionable moire patterns. Now, FM screening goes way back to 1976, but Gary argues that "it wasn't until the introduction of Agfa's CristalRaster in 1993, that this technology became suitable for high quality work."

Thus, desktop publishing, CTP, and FM screening were the final enablers that made it possible for engineers to scan in image files, play with them on a computer with enough horsepower to do interesting stuff, send out the files to have plates made, and use those plates for high quality printing. The playground for innovation was opened.

By the late 1990s, we had all the technology in place from multiple vendors for expanded gamut printing. Separation software was available from Kodak, eder, Opaltone, ICISS, and Pantone. Inks were available through Pantone or Opaltone, or from your local ink vendor. Even Adobe jumped on the bandwagon. Postscript 3, which became available in 1997, included support for HiFi color.

Look out!! The expanded gamut ink train is coming through!

But...

Don Hutcheson wrote a "state-of-the-market" article for GATF World in 1999. His first sentence: "Despite a splashy introduction in the early 1990's, HiFi color printing has grown very little in the last five years."

Hexachrome was well known, but was it a commercial success? It was estimated in 1999 (Hutcheson's article) that Hexachrome was in use by only a few hundred printers. Bear in mind that at this time, there were tens of thousands of printers. Another article (from Glynn Hartley) said in 1999 that "there is a perceived low take up of Hexachrome".

In the same article about Glynn, he reported that there were "over 100 ICISS users currently operating in the UK." Maybe the software sold for the equivalent of $1000 a copy? I would call this a moderately successful small business. I don't want to appear to disparage him, but this is still a small business.

Hexachrome was discontinued in 2008, but Opaltone is also still around. They have their niche in the digital printing market. But they are not a huge company. ICISS is also still around today, but I don't see 100 employees on LinkedIn.

So what happened?

Expanded gamut was showing so much promise. Why didn't it fulfill the hype and become the default printing technology?

Here is an adage which is important to developers of new products: People are generally not willing to pay more for higher quality. There may be niches where the extra cost is justified, but if you want a product to hit prime time, look for ways to make it cheaper. Better yet, look for ways that it can save your customer money.

Adding a few more inks may make prettier pictures, but it will cost more. Prettier, but more expensive pictures are definitely in the niche bucket.

Kevin Bourquin has pointed to another issue that held expanded gamut back in the 90s: "I think the problem in 1994 was that while there were patents about how to do separations and some software to help, it was not well integrated into the production workflows. This made it cumbersome for companies to keep streamlined workflows." Having software to do the color separation is super cool, but you also have to be able to design, create a proof, do the RIP (with FM screening), set up profiles and plate curves, and do process control at the press side. Finding a collection of software together from multiple vendors to do something new can be a challenge.

So what finally happened?

In 2013 Mark Mazur conducted a survey that estimated that 10% to 20% of printers in the flexo world were using extended gamut. Don Carli's prediction came true, but about 15 years later than he predicted, and only within one segment of the print market.

More recently, the percentage has been soaring. Dawn Connell (Brand Marketing of Snyder’s Lance, who own Snyder’s pretzels, Jays, Kettle, Pop Secret, and Archway, to name a few) spoke at the Flexographic Technical Association forum in spring of 2016. In her presentation she said that 85% of their work is expanded gamut. 


In 2016, Kevin Bourquin of Cyber Graphics told me that they have 5500 SKUs separated for expanded gamut. I just checked back with him. As of April 30, 2018, the number is 8615. I should also mention that Kevin spoke on expanded gamut at the FTA Forum conference in Indianapolis on May 7, 2018. (Rumor has it that he mentioned my blog.)

Kevin's presentation isn't the only presentation on expanded gamut at a high profile conference. I just got news that Mike Strickler will be speaking on the same topic at another big print conference at the end of September / beginning of October. This won't be just a quick twenty minute thingie. He has a whole seminar. Smart guy, this Mike fellow. We taught each other everything we know.

Having guys with these credentials... speaking at such prestigious conferences... How can you say that expanded gamut is not a big thing now?!??!

It's not about pretty pictures

Why this huge recurrence?

Kevin points to another enabling technology: "But the first real tipping point was about 2004. Digital flexo plate had gotten a lot better and could print somewhat consistent if you tightly controlled to process. At the same time Esko and Kodak at the Drupa show, committed development resources to ingrate these tools into the workflows that people used to push files." As you can tell, Kevin is big on this whole workflow thing.

Mark and Kevin both pointed to one major snack food company that was an early adopter. Frito Lay was aggressively pushing to drive cost down and quality up. It's tough to meet both of those goals without doing some retooling.


But enabling technology doesn't necessarily translate into market success. Companies need a reason to want to invest in change. According to Mark Samworth of Esko, "The number one way to reduce costs in packaging printing is to reduce the use of custom spot colors." He has no idea whether this is true or not, but he did say I could quote him on this.

It probably seems like ages ago that I mentioned that Kodak jumped back into the expanded gamut in 2011 market with Spotless. (Scroll back if you don't remember.) The name is pretty clever, really. The word means clean, but literally, it means without spots. The pun refers to the fact that expanded gamut printing can be used to replace the icky-dirty practice of spot color printing. Roughly 90% of the Pantone book of spot colors can be printed as a halftone of CMYKOGV.

This saves money. In an old-school print shop, the printer would print the first job of the day with CMYK plus a couple of spot colors. To switch over for the second job, the print units with the spot colors need to be cleaned out to put in a few other spot colors. Cleaning out the print units takes time. Furthermore, the left-over ink can't be just poured down the drain. It has to be stored in buckets for future jobs. I have seen shops that have invested a lot of money just in shelving units to store leftovers. 

Cleaning up after a spot color ink party takes time

With expanded gamut printing, the mixing of inks to make spot colors occurs not in the ink kitchen in buckets, but rather, on the press with halftone dots. Hence, there is no need to clean out the CMYKOGV print units between jobs.

I spoke with Steve Balschi (who is a prepress guy at PrintPak, huge packaging printer), who said that they have plants where all they print is expanded gamut. Steve went on to explain that they had three type of expanded gamut jobs: 1) jobs where only spot colors are printed expanded gamut, and images are left CMYK, 2) jobs where spot colors and images are converted to expanded gamut, and 3) jobs that are a mixture. Whenever possible, they do not convert the images. But why would they want to? They're trying to match an image that was printed with CMYK. The best way to do that is to print CMYK. This underscores my point that it ain't about prettier images.

A further savings comes from the ability to gang jobs, as illustrated in the image below. Multiple related products are printed on the same press as one run, rather than as multiple smaller runs. The same amount of printing, but with only one make ready.

Choco Lotta is one of my biggest sources of snack foods

Spot color replacement is big not only in and of itself, but it enables this gang printing which is like, way big. John Elleman commented on LinkedIn: "[Spot color replacement] is most commonly used for creating flavor/form coding across multiple packages allowing gang printing all on one form versus sequential printing with spot colors, which increases cost for extra printing plates and change over time on press." Kevin Bourquin had a similar comment: "The true benefit is the economics involved in running multiple jobs in combo after replacing all the spot colors."

When has an idea's time come?

Thanks for sticking it out through this long and boring dissertation about the history of expanded gamut printing. We finally get to the moral of this series of blog posts.

In the previous installment (and the addendum) we see that just having a clever idea doesn't make you a millionaire. Unless of course that clever idea is to marry into a hugely wealthy family. In the first part of this blog post we see that a clever idea with a slick implementation is also not necessarily a ticket to the Filthy Rich Club. 

Here is the moral: An idea's time comes when the idea meets up with both the enabling technology and the need. I put that in italics to remind people to quote me on this. The idea of printing with inks in addition to CMYK is a clever idea. Desktop publishing, FM screening, high quality plates, and a full workflow solution are all enabling technologies. Replacement of spot colors was the need that made this idea worthwhile.

When an idea's time has come

Acknowledgements

Normally, I just make stuff up for my blogs. In this case, I thought I might try something a little different. I would like to thank the following folks for making sure my facts were as factual as possible: Don Hutcheson, Mark Mazur, Steve Balschi, Kevin Bourquin, Gary Field, Robin Myers, Mike Strickler, and Mathew Bernasconi.

References

Bernasconi, Color Printing Process and Product, US Patent #5,751,326, filed April 5, 1995

Bernasconi, Color separation and reproduction method to control a printing process, US Patent 8,064,112, filed November 22, 2011

Boll and Gregory, Color-to-ink  transformation for extra-quarternary printing processes, US Patent 5,563,724, filed October 21, 1994

Carli, Don, and L. Mills Davis, High Fidelity Color Rendering and Reproduction, TAGA 1991

Cooper, Process for creating five to seven color separations used on a multicolor press, US Patent 5,687,300, filed March 27, 1995

Eder and Maerz, Producing colour printed image from scanner, German Patent #4,417,449, filed November 23, 1995

Hartley, Glynn, PrintWeek, Bespoke HiFi provides value added market for print films, December 10, 1999

Herbert and DiBernardo, Six-color process system, US Patent 5,734,800, filed November 29, 1994

Hutcheson, Extended density color printing, US Patent 5,528,377, filed March 29, 1994

Hutcheson, Dom, HiFi Color Growing Slowly, GATF World magazine, 1999

Linotype-Hell, High Fidelity Seven Ink Printing, 1994
http://www.greenharbor.com/LHTIfolder/lhti9405.pdf

Plettinck and Van de Capelle, Method and a device for generating printing data in a color space defined for non-standard inks, US Patent 5,689,349, filed April 29, 1994

Politis, Anastasios, et al., Extended Gamut Printing: A review on developments and trends, 1st International Printing Technologies Symposium (PrintInstanbul 2015)

Wolf, Kurt, PS imagesetter: a reasonably priced entry with the Linotronic Mark series, 1995
http://xmedia.biz/home/page.aspx?page_id=550&archive_type_id=92&person=0&categories=&archive_id=2981&from=611&keyword=