The Cellar Image of the Day

Credit and copyright Tony Cook and used with his permission. This was the Earth Sci pic of the Day a week ago. Taken on Tenerife in the Canary Islands, it's a great photo and also shows an interesting phenomenon - at the top of the sun, a green flash appears. This green is not on the sun itself, but a product of how the atmosphere affects the light. From the ESPoD explanation:

More pics of green flash.

http://www.polarimage.fi/sun2/ataulu2b.jpg

I must say that this fella's website has the most incredible collection of sky / weather / water pictures. It was a BIG time sink for me when I came across it.

Enjoy!

I understand the color bit, but I wonder why the edges are so rough. Almost looks like an overexposure. Very beautiful to say the least.

Didn't we see a similar image a while back, I seem to remember something similar...

Quote:

Originally Posted by cweekly

another note bene: this is also related to the reason sunsets are so pretty: the red and orange hues are caused by the lengthening of ths sun's rays as the sunlight travels further, it's in effect being stretched, and longer wavelengths are more red, while shorter ones are more blue. (this "redshifting" is an example of the doppler effect, which also explains why car engines sound higher pitched as they race towards you then suddenly lower as they recede)

that's the gist anyway (from memory),someone else may post a more technically precise answer

Thanks for the lessons, Guys. It does make sense, even to me. It seems like the sunrise & sunset would look almost alike, but sunrises are always loaded with yellows, golds, and oranges while sunsets are filled with reds and purples. A great gift nature has given us. I hope to enjoy thousands more at each end of the day. Imagine trying to explain how a beautiful sunset looks to a blind person who has never seen one. Now that would be a challenge.....

I wonder if the temperature of the air causes the sunrise/sunset color difference. In the morning, the sunlight is advancing through cold night air, and in the evening it is retreating through warmer daytime air.

Ah ha! So that's why when I mixed all the jars of poster paint together, I got brown instead of white......or even black. Also a ration of crap from Mrs Midyet.

Superb explanation, linknoid. That explains a lot of things that didn't quite jibe with what I'd been taught. Thanks for taking the time to expand on it so we could all understand it.
YOU, yes you, lurking out there. You didn't know that either, did you? You were waiting for me to make a fool of myself so you could find out the straight skinny. That's OK, I do it all for you. Happy New Year.

btw- Great link...I'm saving that one.

XOB:

This picture shows an example of the additive color mixing. The most striking example of this I ever saw was in the Hard Rock Casino in Las Vegas. There was a white wall with some cast metal letters mounted on it and the letters all had shadows of different colors. It just about drove me crazy. My poor brain was trying to reconcile the proper shape and angle and area for all the shadows with the obvious problem that they were not "dark". This image recreates the effect as well as any simple 2d picture can.

Here is the link for the science behind the image.

http://www.newtrier.k12.il.us/academ...t/coloshad.htm

EDIT: I found a picture and an explanation I like better.

http://www.exo.net/~pauld/summer_ins...ploration.html

as an artist , I'm compelled to post:
you cannot acheive, (w/ paint & canvas) what I'm reading here. One cannot confuse the spectrum of color with what is created with physical color mixture. The color spectrum is a basic guideline to the physics of color, which is scientifically the explanation to "everything that shallow people will relate to". There are no limits to color and the effects on the mind. Which is to say.... what you may see is not what someone else will see. I've tried some mixtures as suggested in this thread, and if You'll do the same you'll realize that it is totally hypothetic and "textbookish". Color, let alone art, is what is absorbed in one's mind & their imagination. What looks green to me may be teal to you. What is provocative to you may be calming or docile to me. In the minds eye, of course. There is no scietific proof that we even see color at the same level or hue or tone, etc. Especially intensity. Color is a very personal thing. " I saw red" may mean to you that you were really pissed while to someone else may mean they were totally elated.

When you are dealing with color, shitcan the spectrum. It is totally scientific and has absolutely no imagination, preferences, or emotional feelings. ART as well as color is a very personal thingy. That's all I've got to say about that...............

Quote:

Originally Posted by capnhowdy

Quote:

Originally Posted by linknoid

As a physicist (well not really, but I did major in it in college for a while), I would say that you're correct (at least in this comment, the next one where you say to throw out the spectrum completely is going overboard). In my explanation I specifically avoided going into the complexities of perception or even the details of what happens when you mix color. The point was to explain the basics of how colors work to someone who claimed not to know hardly anything about it.

Each person's eyes respond to slightly different wavelengths. In fact, some men only see 2 shades (they're colorblind), and some women actually, because of genetic issues, have 4 types of cones instead of 3, and they actually see a much different colors (and they're genetics mean if they pass on the genes that produce 4 colors for them, their sons will be colorblind).

But once you get past the issue of how each person responds to the various (and infinite) combinations of the colors of the spectrum, then you have to deal with where that combination of wavelengths and intensities are coming from.

First you have the light source. Each different source is different. The sun produces a relatively complete visible spectrum, resulting in very white light, but by the time it's passed through the atmosphere, a lot of the blue end has been scattered out, and even then the spectrum changes based on the time of day, the weather conditions, the pollution in the air, etc. And there are many other different light sources: incandescent lights, LEDs, mercury vapor lamps, halogen lamps, candles, wood fire, arc lamps, flourescent lamps, and the list goes on. None of them really produce a pure, even spectrum, and each one of the wavelengths it puts out interacts differently with different materials.

Then once it's produced by the light source, it has to deal with absorbsion (and re-emission as other colors), reflection, refraction, transmission, scattering, interference, and who knows what else. So when you mix two paints, you have to account for all those other things if you really want to know what color you're going to end up with. The thing the printing industry tries to do is simplify everything enough that they can reproduce most colors based on just a few, for practical reasons. Which is why we use primary colors. But that's definitely not the whole story.

So I hope you'll forgive me for make the vast simplifications to make the mixing of colors understandable and not overwhelming.

thanks for the clarifcation/correction, linknoid
(sorry xobruce, didn't mean to lead you astray)

so I do think I was right about the striations, but yeah was off base wrt the doppler effect's relevance to the colors. didn't quite jibe with me either, glad to get to the root of it.

"crippled but free, I was blind all the time I was learning to see..."

That's OK, cweekly. That's what we do here, run it up the flagpole and see if it gets shot at.