Wednesday, January 30, 2019

The Color Name Conundrum

This article was flagrantly stolen from my keynote presentation at ISCC/AIC Munsell Conference, July of 2018, and from the ISCC Newsletter of January, 2019.

It’s a common argument that my wife and I have. We are at a store or movie or coffee place, and I will comment on another woman’s blouse. “Hey, Honey. Look at the woman in the turquoise top. Isn’t she cute? … She smiled at me… And she handed me a card with her number on it.” Madelaine will invariably respond with “That’s not turquoise!” She may say that it’s teal, or aqua, or beryl, but she will never agree on the color name that I chose. I can blather on all I want about how I am a world-famous color scientist who was asked to give a keynote for the Munsell Conference. It won’t matter. What do I know about color?

The lady in the allegedly turquoise top

This time, I decided that I would win the argument. I started with Merriam-Webster’s dictionary since it is an authoritative reference that would show I was using the color name correctly. This dictionary defines turquoise as “a bluish-green color”, and follows up with the full and much more explanatory definition “a light greenish blue”.

I exercised due diligence and spoke directly with the person who wrote the full definition, Kory Stamper, to help resolve the argument with my wife. She politely (and wisely) declined to get involved. But I could tell that she was agreeing with me.

[As an aside, the exciting thing about attending ISCC/AIC Munsell conferences is that eminent chromo-lexicographers like Kory might be in the audience when they are called out in a keynote address.] defines turquoise similarly: “a greenish blue or bluish green color”. The Oxford English Dictionary provides a similar definition but leans more to the greenish side: “a greenish-blue color”. So, it seems we have a consensus between the dictionaries. But more importantly, we have a consensus in which I win the argument!
The image below shows blue, greenish-blue, bluish-green, and green. The blouse is definitely close to bluish-green, so turquoise is indeed an appropriate descriptor of the blouse color. Did I mention that I claim victory?

The happy shades between blue and green

But I decided to check one last dictionary, Webster’s Third New International. The definition in this dictionary is at once beautiful and tedious.

1) a variable color averaging a light greenish blue that is deeper and slightly greener than average turquoise blue, and greener and deeper than average aqua or average robin’s-egg blue (sense 1)

My stalwart research assistant suggests that the definition might be a bit too complicated

You can see that our puppy, Mozart, was puzzled when he read it, so I diagrammed the definition out for him (see next image). He thanked me when he saw the diagram, and went off to bark a friendly greeting to a squirrel that was outside. By the way, Mozart is not named for Hank “the Tank” Mozart. You will recall that Tank played defensive hatchback for the Green Bay Bruins. His claim to fame is that he scored the winning basket over Jack Nicklaus in the 1968 War of the Roses Tournament. Madelaine and I named the dog after the less-well-known Wolfgang “Wolfie” Mozart.

An Applied Math Guy reads the dictionary

In most dictionary definitions, the lexicographer works to define complex words in terms of more basic words. The Webster’s Third definition of turquoise is unique in that it defines the color relative to other colors which are just as non-basic as turquoise. To really make sense of this tortuous definition of turquoise, I realized that I had to generate similar diagrams for aqua and robin’s egg blue and turquoise blue and greenish-blue, and then for each of the other colors that were called out in those definitions. It only took me three days to generate the following table that delineates the territory of the ten tones in the turquoise tautology. It is clear from this that color names are very precisely defined.

A handy reference for color names in the blue-green family

But I still wasn’t happy. The intertwined definitions haunted me. Where Kory is the Steinbeck of chromo-lexicography, whoever wrote the lovely and sadistic color definitions from Webster’s Third was the Faulkner. I simply had to find out who this anonymous author was.

Luckily, it didn’t take long. The list in the front of the dictionary of contributing experts provided me with the answer. It had to be Isaac Godlove.

[As an aside, the exciting thing about attending ISCC/AIC Munsell conferences is that the audience will recognize the names of prominent researchers in color when their names are mentioned in a keynote address. Let me tell you, the cheers were deafening! Everyone recognized that Godlove was the third author of the seminal paper “Neutral Value Scales. I. Munsell Neutral Value Scale” from the Journal of the Optical Society of America in 1933.]

Of course, some of the people cheering also recognized that Godlove was the director of the Munsell Research Laboratory from 1926 to 1930. What an enormous coincidence that he should get mentioned in the keynote at the Munsell Conference! A few chromo-historians in the crowd actually knew that Isaac Godlove was the chair of the ISCC Committee on Measurement and Specification in 1933. (Note again the coincidence that the ISCC was one of the organizers of the Munsell Conference!)

While Godlove was chair, a group of pharmacists approached Godlove about the need for a definitive guide to color names. This eventually led to the National Bureau of Standards runaway best seller “Color – Universal Language and Dictionary of Color Names”, which became a Broadway play of much acclaim. This absolutely delightful standard carved the Munsell Color Space into 267 regions (called Centroid Colors) and gave each region an intuitive designator like “bG 159”, along with a euphonious name like brilliant bluish green.

A hue slice from the NBS standard on color names

As if that wasn’t enough to earn a prominent spot in my bookcase, the authors dug through all the available color naming guides (like Maerz and Paul, Plochere, and Ridgway) to determine the Munsell coordinates for each of the color words that were defined. As a result, the NBS standard further provides two lists: 1) a list that goes from common color name to the appropriate Centroid Colors in Munsell space, and 2) a list that provides all the color names that have been associated with each of the 267 Centroid Colors.

I was ecstatic. I quickly saw that this book provided a solution to the recurring argument that I had with my wife. The solution is astoundingly simple. Whenever I am within earshot of Madelaine, I just have to go through four simple steps before I utter any color names.

Step 1: Measure the color in question. For example, I called up the woman in the turquoise top, explained the situation, and met her at Starbucks with my spectrophotometer so I could measure her shirt. She understood my predicament perfectly, and agreed to share a Starbucks with me. Her shirt measured CIELAB of 86, -47, -4. Her name is Teal, by the way.

Yes, it’s a bit of a bother for me to carry a colorimeter with me at all times, but what color scientist worth his or her salt doesn’t carry one for the occasional color measurement emergency?

Step 2: Convert from CIELAB coordinates to Munsell designation. One could make use of the Munsell Renotation Data. The official version is conveniently available on the RIT website to do the approximate conversion, but several people have written software that does this. Harold Van Aken (of Wallkill Color) provided a piece of software as a freebie in honor of the Munsell Color Conference. (Yet another astounding coincidence.) Paul Centore has graciously provided an open source conversion, and Danny Pasquale sells an inexpensive tool called PatchTool that provides this function among others. The CIELAB coordinates of Teal’s allegedly turquoise shirt were thus converted to 5BG 8.5/9 in Munsell notation.

[As an aside, the exciting thing about attending ISCC/AIC conferences is that two of the three people who wrote software for this conversion (Paul and Danny) were actually in the audience for the keynote.]

Step 3: Convert from Munsell designation to Centroid colors. It goes without saying that it is pretty quick and easy to leaf through the diagrams (like the one below) in the NBS standard to find the Centroid corresponding to any Munsell designation. In this case, the Centroid Color is 159. Yes, it’s a bit of a bother to carry the NBS standard with me, but it’s a small price to pay for me to prove that I am right in an argument with my wife.

Step 4: Look up the color names listed under the Color Centroid. In the case of Centroid 159, the list is rather short. It includes Beryl Green, Bewitch, Blue Green, Bluish Green, Bright Aqua, Bright Aqua Green, Bright Emerald Green, Bright Green, Bright Jade Green, Bright Turquoise, Bright Turquoise Green, Chill, Crest, Du Barry Blue, Festival, Green, Ice Boat, Light Emerald Green, Lilting Green, Naid, Persian Green, Picturesque, Pool Green, Promised Land, Salome Blue, Song of Norway, Sprite, Sulfate Green, Turquoise Green, Venetus, Venice Green, … and of course, Turquoise. I win!

The fact that this particular color has 32 valid names shows that our assignment of color names to physical colors is not nearly as precise as Godlove and Webster’s Third would have us believe. We need a system like Munsell or CIELAB (or NCS or RAL or Pantone) in order to accurately communicate colors. That’s an important thing to realize, but the more important takeaway from the research presented here is that I won the argument!

May you enjoy arguing with your significant other as much as I do.

If you enjoyed this article, you might consider joining the Inter-Society Color Council! Individual membership is only $50 per year, for which you will receive the ISCC newsletter, as well as reduced rates for any ISCC sponsored conferences.

Such as... the joint TAGA/ISCC conference in balmy Minneapolis in March.

Wednesday, January 23, 2019

Which way is north in Munsell color space?

I wrote a blog post for Inkjet Insight about the Munsell color space. I don't want to spoil it for anyone, but the post is mostly just a gateway post to one about the CIELAB color space. For the Inkjet Insight post, I had my crayons pose for the aesthetically pleasing picture below. I do expect an Emmy for the picture, but I will try to appear surprised when I get called to the stage.

Happy crayons get together for a crayon picnic

Boy! Did that picture stir up a hornet's nest when I posted a link on LinkedIn! Two of my color scientist friends took umbrage. You may be wondering about my choice of the word "friends". Perhaps I use the term loosely, but Danny and Dave are the closest thing I have to friends, I mean, aside from Truffle and Mozart. And I feed Truffle and Mozart twice a day.

Here's Danny's malicious comment: "It seems that you have ordered the crayons as CIELAB would but not as Munsell does."

Dave's equally viscous comment: "Oops. Danny is right of course.  Unless, ... this is a view from below! To be more CIELABish I actually reverse the hue direction in my hanging Munsell Tree."

The gauntlet has been thrown down!!

I gotta ask you gentlemen, Danny and Dave, which Munsell color system you are referring to?

First, there is nothing inherently in the Munsell notation (7.5PB 4/6) that tells us which color points east (0 degrees) and whether orange is clockwise or counterclockwise of red. The Munsell notation for each color includes one of ten designators (R, YR, Y, GY, G, BG, B, PB, P, or RP) to specify a hue family. Within each hue family, there are ten steps which (oddly enough) are numbered from 1 to 10. Each number is one-step change in hue. Thus, 7.5PB is a unique specification for a hue, without any implied orientation.

Take that, Danny and Dave!

Second, there is a disagreement between Albert Munsell and Albert Munsell about the direction of red. As shown in the image below, his 1915 atlas has red pointing at around 45 degrees clockwise of east.

Page ripped from the Munsell Color Atlas of 1915

But in Munsell's New York Times 1919 bestseller "A Color Notation System" the master shows red pointed due north.

More vandalism, but to Musell's A Color Notation System

Both of these Munsell illustrations show orange as being counterclockwise from red. Pretty much the same as the way my Crayolas arranged themselves, and also, the way that CIELAB is arranged. Since there is no "correct" direction for red to point, I feel justified in pointing red to the east.

How do you like the color of them apples, my Dynamic D-named Duo!?!??  Well, I'm not done yet!

Third, the ASTM disagrees with both of these Munsell orientations. In 1968, the ATSM provided us with a "standard method of specifying a color by the Munsell system" (ASTM D 1535). Note that in the ASTM system, red points to the north. This agrees with the second illustration, but hang on a sec while I expound on some ASTM D 1535 trivia that is likely to come up the next time Danny, Dave and I get together for sushi.

ASTM D 1535 dictates this orientation

ASTM D 1535 also assigned a number for each discrete step of Munsell hue angle, from 1 to 100. Interesting point -- their notion of hue "angle" is in centicircs. I just made that word up. One centicirc is 3.6 degrees. It's about time we went metric and got past this silly Babylonian notion that we should measure arcs by comparing against the size of arc that the Earth makes around the Sun in a day. Approximately a day.

The ASTM adopted the obvious convention that 0 Munsellian centicircs would be at 18 degrees counterclockwise from north. I mean... of course. Well... I need to clarify. No one ever really told me whether "true" red was 0R or 5R. I guess I assumed it was 0R.

Also D 1535 is not explicit, but I think that 0 centicrics is not allowed. That has to be called 100. Kinda like the zero-phobia that says that midnight is 12:00 instead of 0:00. And that the first day of a month is 1, rather than 0.

More importantly, note that contrary to "normal" analytical algebra, Munsellian centicircs increment in the clockwise direction! I'm going to report them to their calculus professor!

But hang on. Here's the big thing. Even more importantly, and contrary to Munsell's two books, in the D 1535 system, orange is clockwise from red. O.M.G.!!

Dave boastfully mentioned his "hanging Munsell Tree". Not to be outdone, I provide a picture of my own hanging Munsell Tree. In my case, the world famous Munsell Color Model is joined by the world famous Munsell Color Model Model, Madelaine. We can see that my tree and Dave's tree both adhere to the "orange is counterclockwise from red" convention.

Wild times at the John the Math Guy household

Since there seems to be some latitude in the orientation of the color wheel in Munsell space, I claim that I am well within my rights to orient Munsell space in such a way as to serve as a stepping stone to CIELAB.

For those of you who are wondering about the significance of all this detailed historical research, let me be clear. It's all about me proving that I am right. Nothing else really matters.

NOTE: I would like to thank Robin Myers for pointing out an egregious error in my initial post. I had stated that the Munsell Color Atlas was published in 1913. Robin sent a photo of a page from his very own copy of the Munsell Atlas that clearly shows the date as 1915. (I am so jealous that he has this copy!) I would make up some excuse for why I got this wrong, but it would either be a total "my dog ate my homework" excuse, or it would make me look bad. So, I will just apologize for any pain and suffering which may have been caused by my ineptitude. I am eternally grateful to Robin for finding this embarrassing error, and would like to publicly offer to buy him a cup of coffee or a glass of the most inexpensive beer that can be found, provided he reciprocates by buying me a drink of similar value.

While John the Math Guy, LLC strives to maintain the highest level of scholarly eptitude in all its blog posts, there will inevitably be lapses into complete failure of logic, due diligence, and clarity of exposition. Any liability for anyone actually taking any of these posts seriously shall be limited to any considerations received directly from the party who has his undies in a bundle about this stuff.