The Order of the Stick: Utterly Dwarfed
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    Default What things are violet?

    With digital displays using RPG light, and most print inks only use four colors as well, it's basically impossible to get a picture that emits or reflects violet wavelengths to your eyes. There are probably rare and fancy speciality light sources that produce violet wavelengths, but they would probably be really expensive.

    So the only practical way that I see (haha...) for seeing what the color violet actually looks like, is to look at violet objects under natural light.

    What things are there in nature that reflect a strong violet color (380450 nm)?
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    Default Re: What things are violet?

    Just about any ultra-violet light source should give you a certian amount of violet light - the ones that come with marker kits should work. Two quick examples:

    Obviously, the more powerful ones (like the ones that end up in sun beds) probably aren't good for the eyes, though.

    Also, anything that produces a spectrum (like a spray of water reflecting back sunlight if rainbows are in short supply locally) will give you violet at the end of the spectrum.
    Last edited by Manga Shoggoth; 2019-09-01 at 02:54 PM.
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    Default Re: What things are violet?

    It's entirely possible for an RGB monitor to produce a colour that will look violet to your eyes--it just has to provide the right amounts of red, green and blue to stimulate your colour receptors in the same way violet light would. Where you get problems is when you have a multichromatic light source pretending to be white (e.g. LED light bulbs) reflecting off a violet object, because in that case the colour probably won't look right.

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    ElfPirate

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    Default Re: What things are violet?

    Quote Originally Posted by Yora View Post
    What things are there in nature that reflect a strong violet color (380450 nm)?
    Errrr... flowers? Like various species of... violet, say the Viola Tricolor e.g..

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    Default Re: What things are violet?

    Quote Originally Posted by snowblizz View Post
    Errrr... flowers? Like various species of... violet, say the Viola Tricolor e.g..
    ... I thought "violets are blue"?? Have I been lied to all this time?!

    Anyway, if you can't find any viola flowering at this time of year (which you probably won't in the northern hemisphere), wikipedia also notes lavender flowers and amethyst crystals as being violet in colour.
    Last edited by Ninja_Prawn; 2019-09-09 at 02:21 AM.
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    Default Re: What things are violet?

    Quote Originally Posted by Yora View Post
    What things are there in nature that reflect a strong violet color (380450 nm)?
    The most famous source of violet-purple dye in Antiquity was tyrian purple, made from the murex sea snail.

    Lichen (orcein by the ancient Greeks and Hebrews in the Mediterranean) and other seas critters were also used throughout the world (urchins by Polynesians, purpura snails in Central American cultures) for violet dyes; most paints were made by mixing red and blue colours of varying sources.

    After about the 19th Century, synthetic violet dyes and pigments were invented, which don't really meet your criteria of 'things in nature'.

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    Default Re: What things are violet?

    Quote Originally Posted by Ninja_Prawn View Post
    ... I thought "violets are blue"?? Have I been lied to all this time?!
    You have been lied to. Pretty much everything that is called violet is actually purple. The spectral color violet is the most extreme blue that the human eye can perceive, and has no red component at all.

    Quote Originally Posted by snowblizz View Post
    Errrr... flowers? Like various species of... violet, say the Viola Tricolor e.g..
    Violets can be in any color. Many are white, yellow, or red, and there are lots of shades of blue. What I am looking for is something that reflects sunlight predominantly in the 380450 nm range.

    Quote Originally Posted by factotum View Post
    It's entirely possible for an RGB monitor to produce a colour that will look violet to your eyes--it just has to provide the right amounts of red, green and blue to stimulate your colour receptors in the same way violet light would.
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    As you can see, the extreme end of blue has basically no red or green component. And if you tell a digital screen to use only it's blue LEDs, it will only emit 450-500 nm light, that still activates the red and green receptors. So the brain will process it as a medium blue, not as an extreme violet.
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    Default Re: What things are violet?

    PPG makes some shades of violet paint under the Glidden brand. You might be able to find sample chips of one or more of those shades at Home Depot or a similar store.
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    Default Re: What things are violet?

    If you suspect your color vision is atypical, you can get spectral violet either by refracting light with a high-dispersion prism, or by using a diffraction grating.

    For most other purposes, you can get light that looks like spectral violet, just less saturated, by appropriately blending blue and red light. The "wavelengths of light receptors" chart is a bit misleading, since what matters is the ratio between the responses among the three kinds of cones at any given wavelength, and the chart just normalizes the responses to make the peaks equal.

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    Default Re: What things are violet?

    royal gamma
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    Default Re: What things are violet?

    Quote Originally Posted by DavidSh View Post
    If you suspect your color vision is atypical, you can get spectral violet either by refracting light with a high-dispersion prism, or by using a diffraction grating.
    This is indeed the easiest and cheapest way to create pure violet light. Then just flash it on a white screen and you have it. What is even better, diffraction grates are very easy to come by or make on your own. Even a simple CD will work as a reflective diffraction grate. Once you have that the only issue is to have a narrow light beam so the colors will not mix at the screen, but that can be fixed with a long tube with a reasonably small hole (too small and the diffraction will spread teh light and the ammount of light will be too small anyway) at the end.
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    Default Re: What things are violet?

    Quote Originally Posted by Ninja_Prawn View Post
    ... I thought "violets are blue"?? Have I been lied to all this time?!
    Yes.
    They come in all kinds of colours depending on which species or whatever (wikipedia showed me white, yellow, red, blue and...violet ones). There's even variety within different kinds too.

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    Default Re: What things are violet?

    A small selection of violets.

    When I did my final exams for my gardener apprenticeship this year, I did a report on the cultivation of violets. Seed producers have big catalogues just for violets. The company where I was training bought 93 different variants from the suppliers.

    Quote Originally Posted by DavidSh View Post
    For most other purposes, you can get light that looks like spectral violet, just less saturated, by appropriately blending blue and red light.
    Do you know the RGB value that is supposed to look like spectral violet?
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    Default Re: What things are violet?

    Quote Originally Posted by Yora View Post
    Do you know the RGB value that is supposed to look like spectral violet?
    Wikipedia says you just use twice as much blue as red:

    https://en.wikipedia.org/wiki/Violet_(color)

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    Default Re: What things are violet?

    I've found a source that describes human eyes sensing colors actually like this:



    If that's correct, then blue light does activate the red sensing cells, and the human visual system does indeed make spectral colors look purple-ish. It's a hardware bug.
    Last edited by Yora; 2019-09-03 at 07:41 AM.
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    Default Re: What things are violet?

    Well, the human eye is also capable of seeing colours that theoretically don't exist (at least as single-wavelength entries on the electromagnetic spectrum). Magenta, for instance, a mix of pure red and blue on the RGB chart, doesn't actually appear anywhere in the spectrum, but you can see it just fine.

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    Default Re: What things are violet?

    Quote Originally Posted by factotum View Post
    Wikipedia says you just use twice as much blue as red:

    https://en.wikipedia.org/wiki/Violet_(color)
    Wikipedia goes into a little more detail on approximating spectral violet here.
    Generally, any attempt to render a spectral color with an RGB display will not be as saturated as the spectral color.

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    Default Re: What things are violet?

    Quote Originally Posted by Yora View Post
    Do you know the RGB value that is supposed to look like spectral violet?
    The thing about spectral colours is that they have one peak in the spectrum.

    The non-spectral colours have two peaks (or more), both in the visible spectrum, but the average is not in either of the peaks, so that average as a spectral colour with one peak does not look like the whole spectrum image of the non-spectral colour. Magenta is the prime example, but all of the magenta-like colours are like that, I think most purples are like that.

    (somewhat ninja'd by factotum).

    There are almost certainly colours with more than two peaks in the spectrum, probably most colours are like that. Sodium has two orange peaks and maybe another weak one? but the d lines are so strong and so close together that the colour emitted by sodium lamps appears to be purely orange.
    Last edited by halfeye; 2019-09-03 at 02:03 PM.
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    Default Re: What things are violet?

    Quote Originally Posted by factotum View Post
    Well, the human eye is also capable of seeing colours that theoretically don't exist (at least as single-wavelength entries on the electromagnetic spectrum). Magenta, for instance, a mix of pure red and blue on the RGB chart, doesn't actually appear anywhere in the spectrum, but you can see it just fine.
    Relevant to the discussion of how our eyes work: Why blue light and yellow light don't make a different color:
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    Default Re: What things are violet?

    Quote Originally Posted by Yora View Post
    As you can see, the extreme end of blue has basically no red or green component. And if you tell a digital screen to use only it's blue LEDs, it will only emit 450-500 nm light, that still activates the red and green receptors. So the brain will process it as a medium blue, not as an extreme violet.
    There are some high end OLED TV sets that have a 4th pixel that produces actual violet light. It is generally used to produce super deep blacks though, rather than produce violet light alone.

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    Default Re: What things are violet?

    Perhaps just by a single wavelength LED that emits the frequency you want? Like these 450nm ones?
    https://www.mouser.com/Optoelectroni...z0yt3kZ1yzs64u

    The data sheet for the first one puts the spectrum 440 and 460nm. So that's a pretty tight spectrum and you can buy them at any 5nm increment from 275 - 750nm.

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    Default Re: What things are violet?

    I assumed O2 plasma emmitted violet light, but looking at the spectra I guess it is also actually purple?


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    Default Re: What things are violet?

    I got another color question.

    What is brown?

    If you mix all colors together, shouldn't it be some kind of gray? Where does brown sit on a color wheel?
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    Default Re: What things are violet?

    You only get brown by mixing all colours together when you're talking about pigments. (Mixing all colours together in visible light produces white). If the CMY pigments you had were absolutely perfect then mixing them together would produce black, since the pigments would absorb all incident light--however, those pigments are *not* perfect, which is why you get a sort of muddy brown colour instead and why they have to add the black ink to provide better blacks in the image. (Many years ago I had a very cheap inkjet printer that did *not* have a separate black ink, and as you might expect, the results of printing anything to it were not great).

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    Default Re: What things are violet?

    Quote Originally Posted by Yora View Post
    I got another color question.

    What is brown?

    If you mix all colors together, shouldn't it be some kind of gray? Where does brown sit on a color wheel?
    It would be gray or black only if the proportions are exactly even. You get brown from dark orange broken with a bit of blue.

    edit: in terms of light mixing - not pigments.
    Last edited by Radar; 2019-10-07 at 08:00 AM.
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    Default Re: What things are violet?

    Quote Originally Posted by Radar View Post
    It would be gray or black only if the proportions are exactly even. You get brown from dark orange broken with a bit of blue.

    edit: in terms of light mixing - not pigments.
    Also pigments.

    Back when I built plastic model cars when I was around 12-13, the Testors brown paint (in the small bottles) was a watery runny mess that never covered even with multiple coats. So I had a book that talked some color theory, and showed that brown was basically "grayed orange" made by adding its complimentary color to it.

    So I took some Testors orange and started adding blue until I ended up with a very satisfying brown that actually painted on very well and only required a single coat.

    Mixing all the paints together usually is unbalanced in some way away from neutral gray, so it will depend and not always end up "brown".

    For RGB brown, you could color pick a lot of the elements from the GITP page to see what ratios come up.
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