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Old 3rd December 2019, 05:57 AM   #121
ahhell
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Originally Posted by Puppycow View Post
Yeah, me too. If you look up images for "dress blue uniform" (US military uniforms), they mostly all appear to be black to me. They are actually "navy blue" but it's such a dark shade of blue that it appears black to my eyes. (Like this, for example)
Depends on which uniform. In my day, Navy Dress Blues were black, in my dad's day they were actually a very dark blue. The linked example, is black by most definitions. Only the US Navy calls that color blue.
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Old 3rd December 2019, 06:11 AM   #122
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Originally Posted by ahhell View Post
Depends on which uniform. In my day, Navy Dress Blues were black, in my dad's day they were actually a very dark blue. The linked example, is black by most definitions. Only the US Navy calls that color blue.
And photos depend on the camera, white balance settings, etc. The example image shows dark grays, around RGB 12, 12, 12 in the lighter portions I sampled, with some variations from JPEG compression but no overall blue tendency. The original cloth may have been a dark blue that got automatically white-balanced into oblivion, though.
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Old 3rd December 2019, 06:52 AM   #123
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I have my own set of Marine Corps Dress Blues. The material is definitely black.
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Old 3rd December 2019, 07:03 AM   #124
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I would like to ask a question by phrasing this discussion in the following. A white light source dispersed by an ideal prism will yield a continuous spectrum in terms of wavelength. Yet most people will perceive this spectrum not as continuous but as groups of more dominant colors connected by transitional colors that are mixes of these dominant colors. In the USA probably red, orange, green, blue, maybe indigo and violet (Roy G Biv) are the dominant perceived plus red-orange, yellow-green, etc. in some cases a transitional color become important enough to get its own name, e.g. orange.

Accepting other cultures would name these colors differently and might not have specific names for some, are they actually perceiving the boundaries, and thus the dominant colors vs. transitional colors, differently, i.e. is green a transitional color to them and therefore not worth naming individually (it is perceived as and named as yellow-blue)? And of course the names can come first and influence how this colors are perceived as dominant vs transitional! Or do they see the dominant vs. transitional color boundaries as I would but simply have no word for green because it is not important enough to them? I tend to favor the first hypothesis.

Last edited by Giordano; 3rd December 2019 at 07:08 AM.
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Old 3rd December 2019, 07:47 AM   #125
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I think in this case it's really problem of Japanese language, and not color perception. Aoi does not simply translate to blue. It has wider meaning. I think about it more like 'pale'.

Check all uses here: https://jisho.org/search/aoi

It can be used for grass, and it means it's good looking, or unripe fruit. Based on this article there are also some historical reasons:

https://www.mentalfloss.com/article/...-instead-green
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Old 3rd December 2019, 08:06 AM   #126
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CIE 1931 xy chromaticity space, with black body radiator (pretty much incandescent light bulb) at various temperatures:

There's an ISO (and DIN here in Germany) specification for traffic lights which defines some area inside this color space that lights should fall into. Sorry, I can only find paid sources for that. Here in Germany (probably throughout EU) that defines the color of lights (both for fixed installation and for lights on vehicles) to conform with traffic law.

(The specs list three or so math functions defining lines inside that chart that form the boundaries of the allowed field. With a black body radiator [incandescent light], you see it might be difficult to get a light bright enough that's also definitely green, so the allowed area might go a bit into the cyan or blueish. With modern LEDs, it should be easier to get a bright emitter that's also firmly in the correct color area.)
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Old 3rd December 2019, 08:49 AM   #127
ahhell
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Originally Posted by cjameshuff View Post
And photos depend on the camera, white balance settings, etc. The example image shows dark grays, around RGB 12, 12, 12 in the lighter portions I sampled, with some variations from JPEG compression but no overall blue tendency. The original cloth may have been a dark blue that got automatically white-balanced into oblivion, though.
All that may be true but US Navy Dress Blue uniforms are actually black by any standard outside of the US Navy.

I have seen them in many lighting conditions first hand. I've compared them to my father's version which were very dark blue.

I still have my peacoat, which the Navy describes as navy blue, it is also still very black even after 20+ years. Its an on going joke that my wife loves*, any time she calls anything navy blue I disagree and say it isn't dark enough.

*If by love I mean, wishes would end, she doesn't understand that jokes only get funnier if repeated.

Last edited by ahhell; 3rd December 2019 at 08:58 AM.
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Old 3rd December 2019, 11:01 AM   #128
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I can't believe it's been four pages, and nobody has posted the relevant xkcd yet.

https://blog.xkcd.com/2010/05/03/color-survey-results/

Originally Posted by xkcd
First, a few basic discoveries:
• If you ask people to name colors long enough, they go totally crazy.
• “Puke” and “vomit” are totally real colors.
• Colorblind people are more likely than non-colorblind people to type “**** this” (or some variant) and quit in frustration.
• Indigo was totally just added to the rainbow so it would have 7 colors and make that “ROY G. BIV” acronym work, just like you always suspected. It should really be ROY GBP, with maybe a C or T thrown in there between G and B depending on how the spectrum was converted to RGB.
• A couple dozen people embedded SQL ‘drop table’ statements in the color names. Nice try, kids.
• Nobody can spell “fuchsia”.
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Old 3rd December 2019, 11:06 AM   #129
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The wavelengths absorbed by pigments often do not precisely match the wavelengths in the illuminating light, so the color they actually appear can vary with the light source. My car looks quite black in sunlight but a dark, dark green under fluorescents in my parking garage.
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Old 3rd December 2019, 11:12 AM   #130
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We've had black cats. If you look very closely in good light they are extremely dark brown.
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Old 3rd December 2019, 12:30 PM   #131
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Originally Posted by Trebuchet View Post
We've had black cats. If you look very closely in good light they are extremely dark brown.
It's worse than that, though, because the brown is kind of reddish. So is it really extremely dark brown, or extremely dark russet? Meow.
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Old 3rd December 2019, 10:31 PM   #132
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This discussion reminds me of an experiment I had my students do in university physics classes.

Have a large grid of 5x5 squares of different colors. They should be fairly large. Each square should be about the size of a face. You also need 3 light sources that you can vary their individual intensities. One is red, one blue and one green. You also need a photometer to measure the wavelength of light reflecting off of surfaces.

That last thing needed is a large black cloth with a hole cut in it matching the size of the individual colored squares in the grid.

Now, put the cloth over the grid of colors with the hole lined up for just one colored square. And have the lights set to equal intensity. Use the photometer to measure the wavelength of the light reflecting off the exposed square.

Lets say it is a green square and you measure 520 nm for the light reflecting off of it.

Now move the cloth so that the hole is over a different colored square. Then adjust the 3 lights until the photometer indicates that 520 nm light is reflecting off of this new square.

It will, as expected look green since it is now reflecting the same wavelength of light that was being measured from the green square.

Remove the cloth.

It will stop looking green, and all the squares will appear as their normal color. Even though the photometer is still measuring 520 nm off that square, it won't look green anymore, like it did when it was the only square you could see.

Our brains in fact put a heavy emphasis on comparing the different colors we see in our field of view and can correct for bias in the incoming light. To an extent. With a sufficiently biased incoming light you can certainly change what colors we see in the 5x5 grid. But our brain can make surprisingly big corrections to what we see, so long as it has enough different colors to process as reference points.
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Old 4th December 2019, 01:58 AM   #133
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Originally Posted by Molinaro View Post
This discussion reminds me of an experiment I had my students do in university physics classes.
(snip)
Sounds like that "is this dress white and gold or blue and black?" thing from a while back.

Clearly our perceptions of color do depend to a certain extent on some kind of process that goes on in our brains to correct for different lighting conditions, etc.

ETA:
https://en.wikipedia.org/wiki/The_dress
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Old 4th December 2019, 05:50 AM   #134
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Interesting TED talk, mostly about color illusions.

https://www.youtube.com/watch?v=mf5otGNbkuc
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Old 4th December 2019, 04:15 PM   #135
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Originally Posted by arthwollipot View Post
The only objective way to convey that information is by stating its wavelength, which has already been done. Different people will have different words for the same wavelength of light.
Music is another example of this. An infinitely indiscreet spectrum where specific frequencies have culturally dependent names.

It wasn't until IIRC, 1947 that we had an objective definition of A1 (the lowest key on a standard 88 key piano): 440Hz. Prior to that, depending on where you were geographically, different countries endorsed different frequencies in their tuning forks.
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Old 4th December 2019, 04:58 PM   #136
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A1 isn't the lowest key on a piano by a long shot: most go from A0 to C8, though there are many variations from that standard. And it's A4, the A above middle C, that's 440Hz, so the lowest note, A0, is 27.5 Hz in standard concert pitch.

Last edited by ceptimus; 4th December 2019 at 04:59 PM.
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Old 4th December 2019, 11:47 PM   #137
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By the way, little trivia...Did you know that the US time standard station, WWV (which broadcasts on short wave at various frequencies) includes, among other things, a 440 hz tone that you can use to calibrate tunable things.

So far, at least. Administration wants to shut it all down.
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