
The Difference Between ‘Violet’ and ‘Purple’ (2015) - hawski
https://jakubmarian.com/difference-between-violet-and-purple/
======
jobigoud
This has long been a pet peeve of mine.

I don't disagree with it but the colors shown in the article aren't violet,
they are all shades of purple. Spectral violet is outside the gamut of most
RGB color spaces, including sRGB, Adobe RGB, Pantone, CIELAB, etc. Monitors
also wouldn't be able to reproduce it anyway.

The CIE 1931 curve showing a bump in red inside the blue is misleading I
think. It does not represent how the cones react (the article says so in small
print). The L cones aren't excited at all when pure blue or indigo or violet
light hits them. The graph was built to find the best RGB primaries to use in
order to best "emulate" how we interpret colors, so I think it actually
already encodes our bias and general lack of skill at distinguishing violet
from purple.

Similarly many people don't really make a distinction for cyan and just call
it blue or green when they see it.

~~~
NikolaNovak
What would be the best way to get the true spectral violet then - a paint chip
from hardware store?

Also, do you by any chance have a handy link to an actual graph on how cones
react to various spectra of light?

Many thanks!

~~~
joshvm
Either a UV laser/lamp, or you need a broadband light source, like sunlight,
and a filter/monochromator of some kind (either using a prism or a diffraction
grating, or a bandpass filter). You could find something that only reflected
UV, yes, but only if you had a source that emitted UV in the first place. Odds
are most people don't want UV emitters in a screen they look at 6 hours a day.

The point is that you need a source which contains the wavelength of interest.
Monitor leds are red/green/blue and don't emit violet photons. 405nm is
usually somewhat visible, if a bit blurry. Blue leds are usually Gallium
Nitride based which produces more like 450nm.

Look up the photopic and spectroscopic response:

[https://en.m.wikipedia.org/wiki/Luminosity_function](https://en.m.wikipedia.org/wiki/Luminosity_function)

[https://en.m.wikipedia.org/wiki/Photopic_vision](https://en.m.wikipedia.org/wiki/Photopic_vision)

[https://en.m.wikipedia.org/wiki/Scotopic_vision](https://en.m.wikipedia.org/wiki/Scotopic_vision)

~~~
delinka
I see "spectral violet" and "UV" in two different comments. I have the
understanding that "ultraviolet" is past violet and outside the visible
spectrum. So now I have questions...

Do spectral violet and ultraviolet differ? In what way? If something isn't
visible, why does it matter?

~~~
jacobolus
Ultraviolet refers to wavelengths of light which are just a little bit outside
the range which humans can perceive. It is not visible.

Some fluorescent materials can be lit with UV light, because they will
fluoresce at wavelengths we can see. Otherwise, UV lamps also emit visible
wavelengths.

~~~
blincoln
This is a bit of a nitpick, but most people (especially children) can see at
least a bit into UV. With my contacts in, I can see down to about 400-410nm.
With them out, I can see to about 390nm, because the plastic in the contacts
blocks shorter wavelengths. I tested this using a spectrophotometer.

People who have had cornea-replacement surgery and opted for the UV-
transparent corneas can see further into the UV.[1] A child (with young
corneas that haven't yellowed at all) almost certainly can too.

[1] e.g. [http://www.komar.org/faq/colorado-cataract-surgery-
crystalen...](http://www.komar.org/faq/colorado-cataract-surgery-
crystalens/ultra-violet-color-glow/)

~~~
rmilk
Slighly off topic, but UV visibility is important in other species. See this
link for photos of flowers showing how they appear to bees or birds.

The CIE charts don’t really consider how to interpret or recolor data outside
the color space, for example the UV reflection from flowers or astronomy
photos in the UV/X-ray spectrum.

[http://www.naturfotograf.com/UV_flowers_list.html#top/](http://www.naturfotograf.com/UV_flowers_list.html#top/)

------
mcv
Fascinating. I've often thought about how purple relates to violet, but never
really figured it out.

There are of course colours we call violet that we make by mixing red and
blue. For example, the colours in this very article, which use RGB colours to
mix red, green and blue light to create violet. So the violet in this article
isn't "true" violet at all; it's just a faded bluish purple.

So are there real world paints that are actually violet? Or is the violet from
the rainbow something we cannot truly reproduce, and only fake by mixing red
and blue?

~~~
OscarCunningham
White light contains light of all frequencies, so a violet paint that only
reflected a single frequency would look very dark since it would only be
reflecting a tiny proportion of the light that hit it. Even if it reflected a
range of frequencies around violet it would still look very dark unless the
range was large enough to also contain a lot of blue.

If you wanted to see "true" violet, your best bet would be to find a
monochromatic violet light source. A Blu-ray laser would do the trick. But it
won't look any different from the RGB imitation aside from being brighter.

EDIT: Please do not shine a Blu-ray laser directly into your eye.

~~~
rootusrootus
How about a blacklight? The frequency of light you can see leaking through the
filter is 404nm, so that should be a relatively safe way to see what "spectral
violet" looks like, right?

------
ineedasername
I'm surprised this doesn't mention the Sapir-Whorf hypothesis and the work
done by Paul Kay & Willett Kemptom to test this with color labels. Basically
it found that the presence of labels on colors influenced the decisions
speakers of different languages, with different lexical entries for colors,
made when categorizing colors in the presence of labels. However, absent
labels, the decisions made became more "absolute" with respect to the color
spectrum and less subjective, and different language speakers' decisions began
to match each other. [0]

[0] [http://www.blutner.de/color/Sapir-
Whorf.pdf](http://www.blutner.de/color/Sapir-Whorf.pdf)

------
ohduran
Good one, but the part where we as a society collectively define what 'violet'
and 'purple' means is lacking. It's all been covered in a wonderful book
called Through the Language Glass, by Guy Deutsch.

Find my notes on that book on [https://alvaroduran.me/through-the-language-
glass](https://alvaroduran.me/through-the-language-glass)

Edit: fix link

------
dreen
Interesting article

"So, purple is more reddish and saturated, while violet is more bluish and
less saturated."

I'm slightly colorblind and this sentence made me WTF out loud. Purple in that
picture looks way more bluish than violet.

"If you take a look at the distance between violet and blue in the picture of
the spectrum above, it is about the same as the distance between green and
orange."

Since I can easily mistake the colours in any of such pairs I assume that
colorblindness works by "muddying the lines" of spectral representation of
colour? Would that make it a neurological problem rather than an optical one?

~~~
OscarCunningham
I used GIMP to maximally saturate the colours:
[https://i.imgur.com/wfyEWcP.png](https://i.imgur.com/wfyEWcP.png)

Does the purple still look more blue than the violet?

~~~
dreen
Hmmm, no I guess not. If I didn't know I'd just label both as blue.

~~~
jerf
As others are pointing out, it's worth remembering our monitors aren't
necessarily even capable of producing true violet. And I'd add that monitors
vary widely in quality themselves. This one I'm typing on doesn't yell to me
"piece of crap", because I mostly do coding-type activities on it and it's
plenty fine to do syntax highlighting, but sometimes when the rotating desktop
background shows the same one on this monitor and the built-in Macbook
monitor, it's like, huh, there's a lot of difference there. It really wouldn't
be a great monitor to watch media on routinely.

We aren't even all looking at the same colors in the first place.

~~~
dreen
Yeah I get the same impression, it's just that I don't think I could recognise
those as Purple and Violet even in non-oversaturated form, to me it's all just
different nameless hues of blue.

~~~
qubitcoder
I'm not so sure about that. The left side appears _overwhelmingly_ purple, and
the right side looks _very_ blue. Have you tried something like the
Farnsworth-Munsell 100 hue test?

~~~
dreen
Thanks, that was an interesting test. I guess my feeling of "I'm slightly
colourblind" is correct. I don't seem to have that many problems with blue
though.

My results: [https://imgur.com/a/0AvU4hX](https://imgur.com/a/0AvU4hX)

------
myself248
This may also explain why digital cameras have such trouble picking up certain
purple/violet colors but not others.

~~~
jacobush
You mean the hump in the red detectors of the human eye? I had no idea about
this!

~~~
jobigoud
There is no hump in the red detectors. The hump exists only in curves we use
to translate light into RGB, and is there precisely to help translate that
violet into purple.

[https://en.wikipedia.org/wiki/Cone_cell](https://en.wikipedia.org/wiki/Cone_cell)

~~~
tgb
Thanks for pointing this out, thought I was going crazy. So the article's
explanation of why violet and purple look similar even though they are
completely unrelated in spectrum is bogus (the article claims it's due to this
secondary peak in the red cone). So what's the real reason?

~~~
pygy_
Quoting the legend of said picture in the article:

 _" ""Note that this chart does not show the spectral properties of the cones
themselves (but they look similar). It represents the CIE 1931 colour space,
which, simply put, corresponds to the signals after they have been processed
by the brain."""_

~~~
tgb
Quoting the last section of the article:

"""The reason why purple and violet look similar to us is because they
stimulate our cones in a similar way, but _most other animals don’t share the
same types of cones and “post-processing”_. This means that to other animals,
purple and violet may look completely different!"""

Emphasis theirs. This is the part I'm calling out. Stimulation of the cones is
not relevant!

(Of course the cones _are_ relevant but the difference is very much larger and
of a different nature than they make it out to be. Most mammals have only two
color cones.)

------
raverbashing
So, do colorblind people see Violet and Purple "more differently" than non-
colorblind then?

~~~
mcv
I'd expect so. It's simultaneously easy and hard to test. Easy because you
need to show something violet on a similar purple background, and hard because
we're not good at producing violet: computer screens and regular printers
won't work.

------
thraway-burnout
Is this article using Violet to refer to Indigo?

~~~
mannykannot
Of the seven traditional named spectral colors, indigo and violet seem to be
the least distinct pair. Newton may have included it mainly to have seven
named colors, as a parallel to the seven notes of the western major scale in
music. He admitted that his ability to distinguish colors was not acute, and,
after he had selected his seven, he asked others to mark them off on a
spectrum projected on a wall. This is different, of course, then asking them
how many distinct colors they thought best characterized the visible spectrum.

[https://en.wikipedia.org/wiki/Indigo#Classification_as_a_spe...](https://en.wikipedia.org/wiki/Indigo#Classification_as_a_spectral_color)

~~~
OscarCunningham
What I've heard as the explanation is that his "blue" referred to our "cyan"
and his "indigo" referred to our "blue".

~~~
aasasd
Which almost exactly corresponds to the ‘rainbow colors’ as used in Russian
(and probably other Cyrillic languages). The color swatches in the linked
article are precisely Russian ‘blue’ for Newton's indigo and ‘lightblue’ for
blue.

------
pjungwir
Very interesting! All my life I've wondered why sometimes we say "violet" and
sometimes "purple", with a vague sense that they are not exactly synonyms.

Here is a related question that got a very knowledgeable and helpful answer:
[https://news.ycombinator.com/item?id=17507968](https://news.ycombinator.com/item?id=17507968)
(Why is there a color "wheel" when frequencies are linear?) HN is amazing!

------
tambourine_man
Colour Mixing: The Mystery of Magenta

The Royal Institution

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

------
combatentropy
> Purple objects are "red and blue at the same time," whereas violet objects
> are . . . just violet.

Not on RGB screens. If I take a color picker to the page's image of a color
spectrum, said to contain pure violet, it is still a mix of red and blue.

I admit that it is odd that the left end of the spectrum seems to have color
from the right end. It's as if the spectrum wraps around, in our mind's eye at
least.

------
bprasanna
Well the same kind of confusion exist in color books for toddlers. In most
books they show purple color for violet. Or they call violet as purple!
[https://curiosity.com/topics/violet-and-purple-arent-the-
sam...](https://curiosity.com/topics/violet-and-purple-arent-the-same-thing-
curiosity/)

------
JKCalhoun
Had an art teacher tell me that "purple" was not a "color" but rather the name
of a dye used hundreds of years ago. She said "violet" is the name of that
"color" you are referring to as purple.

------
mongol
It is interesting to me that if there would be a way to stimulate red and blue
cones, without stimulating green, you would see a color never seen before. As
there is no wavelength that accomplishes that.

~~~
floatrock
[https://en.wikipedia.org/wiki/Tetrachromacy](https://en.wikipedia.org/wiki/Tetrachromacy)

You've heard of super-tasters? There's a genetic variation that creates a kind
of fourth color receptor in some people, apparently giving them the ability to
perceive colors others can't!

> One study suggested that 2–3% of the world's women might have the type of
> fourth cone whose sensitivity peak is between the standard red and green
> cones, giving, theoretically, a significant increase in color
> differentiation.

------
bregma
What about aubergine?

------
isoskeles
To me, most of these discussions about color come off as, “Weird flex but
okay.” And I don’t care if _you know_ how the human eye perceives color.

There is a distinct difference between how we talk about color and how we
perceive it, and while it’s helpful to understand both (especially if you need
to for your profession), I don’t find it helpful to act like you’re smart for
knowing this. Or similarly, to act like other people are stupid and it’s a
“pet peeve” of yours that they use the word “violet” to describe a color
instead of spectral light. Words can have multiple meanings, and the violet
ship has sailed.

