... we drove off into the sunset looking for another place to put the garbage. We didn't find one. Until we came to a side road, and off the side of the side road there was another fifteen foot cliff and at the bottom of the cliff there was another pile of garbage. And we decided that one big pile is better than two little piles, and rather than bring that one up we decided to throw our's down.
I am quite happy about all the responses I have had to my post on counting the number of colors, ranging from the highly technical to the downright flippant. These responses were posted in a variety of places, and I have decided that one big list of comments is better than five different small lists of comments.
Here's how others answered the question of how many colors there are.
My co-worker Parker Will, who always cracks me up, sent me a link to one person's very imaginative answer. 512 cubic inches. This book simply contains all the colors that are fit to print. It reminds me of a book that may still be in my basement... a book which is a times table from 1 to 999 by 1 to 999.
The RGB Colorspace Atlas
Here are some answers from various LinkedIn groups. I have added some of my own snarky comments.
Nancy Eagan ...as much as there is sunlight ..?
Wei Ji • I think the ultimate question is: how to define "a" colour? the unit that enables us to count how many colours are there.
[Me - Excellent point!]
Mark Taylor • Very thoughtful article. You missed "4" - which is the answer an inkjet printer would give you ;-)
By the way I've also wondered about what the limits of CIELAB space were, and just assumed as a self-taught color scientist I hadn't yet read the right book!
Gary Field - Research on the number of colors issue usually starts with reference to the Dorothy Nickerson and Sidney Newhall paper of 1943 (JOSA, pp. 419-422). They conclude that there are about 7,500,000 surface colors at "supraliminal" viewing conditions, and 1,875,000 colors when viewing conditions approximate those used for color matching work.
Some experimental work of mine (1996 TAGA Proceedings, pp. 14-25) from a printing industry perspective suggested that the offset lithographic process could produce about 1,200,000 colors, while the gravure process could achieve about 1,500,000. A later estimate by Andreas Paul of FOGRA was about 1,000,000 colors for 4-color offset lithography, and around 1,400,000 for seven-color lithography.
Mike Pointer and Geoff Attridge concluded that there were about 2,280,000 discernible colors in their 1998 CR&A article (pp. 52-54).
A "color" could be said to exist when an observer indicates that the perceived new sensation differs from a previous sensation. The "16.7 million colors" touted for color monitors means, in my opinion, that there are 16.7 million different combinations of RGB radiation, but because many of these combinations are visually identical, they are not distinct colors from a human perspective. The estimates reported in previous paragraphs are based upon color difference equations of one type or other. Different equations will produce different results, and the illumination level exerts a powerful influence upon the visual color discrimination task.
A TAGA essay of mine, with more detail and some extra references, entitled "The number of printable colors" appears in a collection published under the title of "Color Essentials - Volume 2" that was published by the Printing Industries of America.
[Me - I am honored to have you comment, Gary. I have one of your books in my bookcase! I have read through your paper, Gary. If I understand correctly, the number is more or less based on the original deltaE formula? Better estimates could be arrived at through DE2000, although this would be a lot of work. I agree with your assessment of the 16.7 million number.]
David Albrecht - There are 4 million colors, give or take a few. This is based on the observations and surveys done over the years for a trained human eye and what it can observe. As Gary points out, a monitor may be able to display more combinations of RGB, but we will only be able to see about 1/4 of the combinations. And according to the rules of observation, if we can't observe them, they do not exist. The "if a tree falls in the woods" concept.
From this 4M or so we drop to untrained human eye, to "compromised" human eye (color blind/deficient), printable colors, etc. It's still amazing that we can reproduce those 1M colors with just 4!
[Me - Nice to have a comment from an old friend. If a color falls in the woods, will someone walk by and return it to the box?]
Gary Field • Adding to David's comment, color discrimination capability for those with normal color vision peaks between the late teens and early 20s. This brings to mind Keith McLaren's observation concerning "correct" color vision; it is "... always that of the observer having the power to accept the batch as a good commercial match".
So, the young do indeed have a more colorful world, but the older people who usually wield the 'OK' stamp of approval, establish the color boundaries.
Alessandro Rizzi • Let me suggest an interesting paper about the impossibility of counting the number of colors:
"Why we don’t know how many colors there are"
by Ján Morovic, Vien Cheung, and Peter Morovic
presented at CGIV 2012 conference this year
Gary Field • @Alessandro: Thank you for that link to the CGIV paper about why we don't know how many colors there are; I found the authors' slide presentation online. Except for very constrained conditions (observer, viewing source; or, if computed, the formula), a definitive, universal number is not likely. I will be happy when claims of "billions" or "a few thousand" colors no longer appear in print (yes, a low bar!).
Arnaud Fabre • Everybody agrees on the fact that the conditions to compute the number of colors are :
- a well defined set of observation conditions
- a perceptually homogeneous colorimetric space
I did not read the paper of CGIV, but I assume that it only ask how we can do serious science with at the basis a vision test applied to 30 persons more or less. And of course Lab is not so perceptually homogeneous, and even with the dE2000 patch, the parameters and the threshold are not so obvious to set.
But it is the only thing we have, right ? and it did not work so bad most of the time. So the basic idea is more :
"how can we compute the number of color that are available with those assumptions ?"
Paul Lindström • John – on DE2000 – What is commonly repeated is that a DE of 1 when using the DE Lab formula from 1976, is a reasonable threshold for where humans with reasonable colour vision see a difference between hue shades (colours). When using DE2000 my guess is that the threshold should be somewhere be between 0.5 and 0.75. Might not sound much of a difference, but using 0.5 would double the number of colours (if my layman use of math is correct).
[Me - Math Guy time... if 0.5 DE were to be used instead of 1.0 DE, the number of colors would go up by a factor of 8, since there would be twice as many in all three directions.]
Ryan Stanley •
[Me - This one below was my favorite. It was posted on the blog itself. Anyone who knew me in my previous incarnation as John the Revelator knows that music has always been a big part of my life.]
we need look no further than Joseph and the amazing technicolor dreamcoat.
the answer is clearly 29 (or maybe 27, or 26 if you're an art teacher).
red and yellow and green and brown and
Scarlet and black and ochre and peach
And ruby and olive and violet and fawn
And lilac and gold and chocolate and mauve
And cream and crimson and silver and rose
And azure and lemon and russet and grey
And purple and white and pink and orange
Newton, phah...Tim Rice and Andrew Lloyd Webber have the answers (except for silver and gold.....oh yeah, and black)