Do water droplets in space alter the colour of sunlight?

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gary byars

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gary byars  asked the Naked Scientists:
Dear Sir/Madam

I have a question which I hope you may spare a moment answer, as a graphic designer I utilise colour theory for print (CMYK) and web design (RGB).

My question is: -
As there are no water droplets in outer space to split the colour spectrum. How is it when you see images taken from outer space, the pictures are in full colour and not a reddish colour or for even a colour camera to work at all, as it’s designed for the human eye?  
My brief understanding

The simplest example of the visible spectrum is the colours of the rainbow. Newton 's Experimentum Crucis show that Blue light is refracted more than red light and so the colours of the spectrum are displaced by different amounts on passing through spherical water droplets.
The humans eye has 2 rods (Shades of grey) and 3 cones (RGB) which detect the colour spectrum on passing through the spherical water droplets (that's why the sky is blue),
Naturally Red travels faster than blue, as blue is the warmest part of a flame and is the hottest colour
I understand that the Hubble telescope sends data which is then constructed onto an image and that the Suns real colour is a greenish brown colour and we view it as yellow, because the light has been split up though water droplets
Garry Byars

What do you think?



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Do water droplets in space alter the colour of sunlight?
« Reply #1 on: 20/07/2009 22:10:27 »
HI gary byars
The sky is not blue just because of water droplets. It looks blue due to the fact that light which is traveling  to nearby parts of the surface are scattered (as when light goes through frosted glass) so we see some light from all directions. Because the amount of scattering is greater for shorter wavelengths, we see more blue than red - the sky looks blueISH. Also, when the Sun is low in the sky and has passed through more air than at mid day, the colour is redISH, beacause more blue has bees scattered away. (Neither the blue sky nor the red sun are very saturated colours, are they?)
Why do you say that the light reaching a camera needs to be 'tinkered with' by the air it is passing through? The best images will be through no air at all. You'll get all wavelengths in their original proportions.

Aha, I think I see what you may be getting at. Why is our vision not pre-corrected for atmospheric contamination?
Well - close objects won't be affected much (they're the most important ones to get right) and even distant ones are only changed a bit (see my first comments) and the brain does its very best to compensate for  the difference between daylight and dusk conditions.

Cameras are not as smart and you need to correct for lighting conditions (sun / shade / tungstes etc.) if you want a photo to look the same as you (and your smart brain) remember a scene. Auto colour balance can easily get it wrong.


Offline Soul Surfer

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Do water droplets in space alter the colour of sunlight?
« Reply #2 on: 20/07/2009 22:38:13 »
You seem to have a very screwed up idea of how light gets its colours and how colour perception works.  It is very difficult to know precisely where to start explaining things and answering your question.  Particularly as you claim to know a bit about how colours are presented in graphic arts.

Let me start with the absolute basics.  Electromagnetic radiation all travels at the same speed (the velocity of light)and can come in a wide and continuous range of frequencies which can range from radio waves to gamma rays. Visible light is just a small section of these frequencies.   There are several different sources of this radiation.  For light there are spectral lines emitted by particular atoms and molecules when they are excited. for example the yellow light emitted by old fashioned sodium lamps or the red of neon tubes.   Continuous radiation emitted from hot solids liquids and gasses like red hot steel and the sun this consists of a broad range of frequencies.  normal light consists of a wide range of these frequencies and coloured objects reflect certain restricted ranges like red and blue.

The fact that water droplets can split light into different colours has absolutely nothing to do with basic colour perception.

It is also important to note that red is the lowest energy (coolest)and blue the higest enegy and hottest part of the spectrum. This is easier t understand that because things start red hot and then get white hot. As a person knowlegable about colorimetry you should know about colour temeperature of light where 3000degrees is the colour of a tungsten light bulb 6000degrees sunlight and 12,000degrees that of blue skylight

« Last Edit: 20/07/2009 22:46:53 by Soul Surfer »
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