
New Map Scale Is More Readable by People Who Are Color Blind - draenei
https://www.scientificamerican.com/article/end-of-the-rainbow-new-map-scale-is-more-readable-by-people-who-are-color-blind/
======
vitalique
I am not colorblind, but work with data visualization in Matlab a lot. This
hilarious SciPy2015 talk[1] convinced me to switch to the Parula color scheme.
There's no way I'm going back to Jet.

[1]
[https://www.youtube.com/watch?v=xAoljeRJ3lU](https://www.youtube.com/watch?v=xAoljeRJ3lU)

~~~
tapia
Shouldn't it have convinced you to switch to Viridis instead?

~~~
vitalique
Yes, Viridis is quantifiably better than Parula, as the talk shows, but Parula
comes with the standard Matlab, and the jump from Jet to Parula was of such a
tremendous magnitude that I kind of fell in love with the Parula color scheme
right away. Jump from Parula to Viridis would be less noticeable, I guess. The
talk opened my eyes to the fact that there are much better ways to use color
for information presentation. (Sorry for the late reply)

------
toomanybeersies
I've been using Color Oracle [1] to simulate colour-blindness as part of my
standard developer workflow recently. For such a common disability, it's
shocking how little work most people put into ensuring accessibility for
colour-blind people.

[1] [https://colororacle.org/](https://colororacle.org/)

~~~
nonane
Thanks for the link. Is the macOS version working for you? I can't get it to
work on High Sierra.

~~~
sogen
Do you have Java installed? It works for me.

There's another app from a Japanese lab but can't remember the name.

~~~
nonane
I can see the app running - but doesn't change the display when I select a
simulator option from the drop down menu. Will play around with it. Thanks!

~~~
LambdaComplex
Maybe it's working just fine but you're already colorblind ;)

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brianmcc
I am always pleased to see annoucements and discussions on colour blindness.

Forgive me for sharing again my writeup on this syndrome from my own
experience, if you don't yourself have any such deficiencies you might find it
interesting!

[https://mcconnellsoftware.github.io/colourblind-in-
software-...](https://mcconnellsoftware.github.io/colourblind-in-software-
driven-world/)

~~~
nonane
Thank you for the write up - this was good to read. Someone close to me was
just diagnosed with color blindness and this was very helpful.

~~~
brianmcc
Thanks! (If you ever see them in a super pale pink shirt, check if they
believe it's white and may've been ruined in the laundry. Been there, done
that)

------
Derbasti
About 8% of all males are color-blind. If you are a scientist, and want to
publish your work, there's a one in four chance that at least one of your
three reviewers is color-blind.

Rainbow color schemes are ridiculously bad. One study showed that medical
professionals who look at rainbow-themed plots every day, immediately made
fewer errors if presented with a simple grayscale plot instead, despite not
having any experience with the grayscale color scheme.

Add to that that human perception is much better at seeing high-frequency
lightness contrast than color contrast. Color contrasts are better-suited for
categorical data.

~~~
nbsd4life
> there's a one in four chance

Closer to 1 in 7, because the reviewer might be female (who are rarely color
blind).

~~~
bradknowles
Closer to 1 in 4, because sadly there are very few reviewers who are female.

------
Terr_
This reminds me of CubeHelix [0], which aims to create scales which degrade
gracefully to grayscale, which also minimizes potential color-blindness
issues.

[0]
[https://www.mrao.cam.ac.uk/~dag/CUBEHELIX/](https://www.mrao.cam.ac.uk/~dag/CUBEHELIX/)

~~~
Terr_
P.S.: Visual examples:
[https://www.mrao.cam.ac.uk/~dag/CUBEHELIX/cubewedges.html](https://www.mrao.cam.ac.uk/~dag/CUBEHELIX/cubewedges.html)

------
uptime
[http://colorbrewer2.org](http://colorbrewer2.org)

“Color Advice for Maps”

Brewer has been on this for a while! Mike Bostock approved. Check “colorblind
safe”

------
pbhjpbhj
With just two colours it's hard to see the intermediate values because our
eyes tend to blur together colours; is that an intermediate value or sharp
edge that I'm seeing fuzzily due to poor focus? With an intermediate tone,
such issues are pushed down to lower resolutions - with yellow-red-blue I know
for sure that if it's red it's an intermediate, but is the orange area a mix
of lots of small yellow and red domains or is it a field of intermediate
domains?

Rinse and repeat.

The article seems to say "this scale is better" whilst also describing how
other scales can be better. The evidence they present says to me "choose
scales according to the data, the desired use, and the observer", of you ship
the data used to cover a visualisation along with that visualisation then
people can use their own scale altered to the purposes (and disabilities) they
have.

~~~
Sharlin
Any scale that only uses hue is terrible, no matter how many intermediate
steps. Scales that only accidentally utilize luminance (due to human vision
being most sensitive to green, then red, and by far the least sensitive to
blue) are only marginally better. Indeed, the rainbow scale is atrocious also
due to the perceptually most luminous color being somewhere in the middle of
the range, so people with red-green deficiency cannot even easily use
luminance cues to make sense of the data. Not even mentioning the fact that
human vision is simply much better at distinguishing luminance differences
than hue differences.

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ebikelaw
This advice is also in Tufte’a first book. This bichromatic scale is given as
an example.
[http://photos1.blogger.com/x/blogger/645/100/1600/834939/Tuf...](http://photos1.blogger.com/x/blogger/645/100/1600/834939/Tufte%2005.jpg)

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DangerousPie
Isn't this almost the same as the viridis palette that has been around for
ages?
[https://cran.r-project.org/web/packages/viridis/vignettes/in...](https://cran.r-project.org/web/packages/viridis/vignettes/intro-
to-viridis.html)

~~~
driax
I just skimmed the paper [1], and their conclusion starts:

> We identified one colormap in particular to be optimal for viewing by those
> with or without CVD, which we name cividis (Figs 4 and 5), generated by
> optimizing the viridis colormap and selecting the J' linearization that
> maximizes the range of J'. We chose this map due to its wide range of
> colors, resulting from a wide range of J0 values while still changing b0
> significantly, and overall sharpness when overlaid onto complex images.

So pretty closely related :)

[1]
[https://arxiv.org/ftp/arxiv/papers/1712/1712.01662.pdf](https://arxiv.org/ftp/arxiv/papers/1712/1712.01662.pdf)

~~~
jfoldager
I'm disappointed that they (in my opinion) managed to make a worse color
scale. If you look at the CVD-Jet color bar you can see blocks that appears
quite similar separated by too sharp transitions. This is a common problem in
e.g. rainbow scales. They highlight them selves that yellow appears as
highligt, yet the highest values get translated to black. How is black
supposed to be interpreted as more luminescent/intense than yellow? It happens
to be a color scale that makes the cells look good, but to me that is
happenstance.

~~~
raphlinus
CVD-Jet is not the new color scale, it's a simulation of what Jet looks like
for certain colorblind users.

To my eyes, cividis (which is the new scale) is good by the numbers, and
there's a strong argument it's more robust for colorblind users, but viridis
looks better.

------
sbr464
I added a basic React component that also has the values in RGB computed

[https://github.com/sbrichardson/react-
cividis/blob/master/RE...](https://github.com/sbrichardson/react-
cividis/blob/master/README.md)

------
masklinn
Related: How Bad Is Your Colormap? (Or, Why People Hate Jet – and You Should
Too): [https://jakevdp.github.io/blog/2014/10/16/how-bad-is-your-
co...](https://jakevdp.github.io/blog/2014/10/16/how-bad-is-your-colormap/)

Also related: seaborn (a helper library on top of matplotlib) has a special
case dedicated to rejecting requests for using jet

~~~
kozhevnikov
Why is it called jet? Can't find any definition/abbreviation for it beside
that it's called jet in MATLAB.

[https://www.mathworks.com/help/matlab/ref/jet.html](https://www.mathworks.com/help/matlab/ref/jet.html)

~~~
IanCal
From some of what seem to be the matlab docs

> The jet colormap is associated with an astrophysical fluid jet simulation
> from the National Center for Supercomputer Applications. See the "Examples"
> section

[http://matlab.izmiran.ru/help/techdoc/ref/colormap.html](http://matlab.izmiran.ru/help/techdoc/ref/colormap.html)

------
sbr464
Here are the RGB values converted from the Matlab color index format
mentioned.

[https://github.com/sbrichardson/react-
cividis/blob/master/sr...](https://github.com/sbrichardson/react-
cividis/blob/master/src/Cividis/RGB_values_example.js)

------
lurquer
I wish the article would have provided the formula for cividis... that is, how
to transform a range of values from 0 to 1.0 into standard RGB values.

~~~
tomsmeding
The "S2 file" mentioned on the liked page gives a look-up table for the
cividis scale:
[http://journals.plos.org/plosone/article/file?type=supplemen...](http://journals.plos.org/plosone/article/file?type=supplementary&id=info:doi/10.1371/journal.pone.0199239.s002)

Apart from the comment on line 1, that file contains 256 lines with a colour.
I suppose to get a finer scale, you can interpolate with any reasonable
function you like since the differences are so small.

------
dwdz
Matplotlib has some nice colormaps as well:

[http://medvis.org/2016/02/23/better-than-the-rainbow-the-
mat...](http://medvis.org/2016/02/23/better-than-the-rainbow-the-matplotlib-
alternative-colormaps/)

[http://bids.github.io/colormap/](http://bids.github.io/colormap/)

~~~
JorgeGT
A plus is that you can easily import these into many programs (MATLAB,
ParaView, QGIS, etc.) thus having a consistent look and feel in your plots.

------
wcfields
Semi-related tid-bit: You'd be shocked how many theatrical lighting designers
over the age of 45 are color blind. Never used to be a workplace issue since
there was only a limited number of gels to place over lights and even then
they were all numbered / catalog.

With LEDs being able to project (nearly) any color the old-guard are facing
some challenges.

------
mark-r
They claim that the new scale gives a continuum from dark to light, but if you
look at the example it goes dark at both ends with the brightest colors in the
exact middle. Why the discrepancy?

~~~
zck
I don't think it does. The picture here:
[https://static.scientificamerican.com/sciam/assets/Image/UPj...](https://static.scientificamerican.com/sciam/assets/Image/UPjournal_pone_0199239_g001.png)
is CVD-Jet, _not_ their new scale. The blue-and-yellow rightmost picture is
described as "as a person with red-green color blindness sees the rainbow
image [in the center]". This scale does put the brightest colors in the
center.

Their proposed scale, cividis, does not have a brightness in the middle of the
scale. It's the second image in the article:
[https://static.scientificamerican.com/sciam/assets/Image/jou...](https://static.scientificamerican.com/sciam/assets/Image/journal_pone_0199239_g005.png)

~~~
nbutyllithium
Correct, one of the links in the article shows a pretty clear comparison
between rainbow scale, how that looks to someone with color deficiency (with
the dark portions on the ends), and their proposed scale.

[https://www.comsol.com/blogs/a-simulation-color-table-for-
en...](https://www.comsol.com/blogs/a-simulation-color-table-for-engineers-
with-color-vision-deficiency) \- midway down the page.

------
dzdt
Did I miss it, or are there zero example images in the article using the new
color scale?

~~~
close04
The yellowish/blueish diagrams _are_ the new scale.
[https://static.scientificamerican.com/sciam/assets/Image/jou...](https://static.scientificamerican.com/sciam/assets/Image/journal_pone_0199239_g005.png)

I always hated rainbow scales because I always see artificial boundaries where
the colors change between 2 contrasting ones.

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jwilk
If you are confused about _ve_ in the table:

+ve = positive

-ve = negative

------
superkuh
The image at the top of the page loads fine. But the rest an so encumbered
with Javascript to load you literally have to reload the page at least 4 times
(to load the JS domain, that loads the JS domain, that loads the JS domain) to
see them.

I gave up and closed the tab.

~~~
mrob
Works for me with JavaScript disabled in Firefox. I'm not seeing anything in
the source that would cause problems either.

