How do 'false colour' images work?

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Offline thedoc

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How do 'false colour' images work?
« on: 11/12/2015 11:50:04 »
Ed Wilson  asked the Naked Scientists:
   What do the colours in a "false colour" image represent?

False colour is used to represent wavelengths outside the visible spectrum, but there's an enormous range of such wavelengths.  If I see a shade of red in two false colour images, does it represent the same actual wavelength?

Is there a recognised standard for false colour representation?  Is there a "spectrum mapping" for different types of observation - the infra-red and the X-ray for example?  Or is it up to the creative inspiration of the person producing the image?

What do you think?
« Last Edit: 11/12/2015 11:50:04 by _system »


Offline evan_au

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Re: How do 'false colour' images work?
« Reply #1 on: 11/12/2015 21:41:11 »
The human visual system and normal computer screens can represent 3 primary colors - red green and blue, in (mostly) 2 dimensions.

Multispectral scanners are often used on satellites for Earth observation and astronomy, and create far more than 3 colors (potentially hundreds), so it is impossible for the human visual system to view them directly.

I expect that most images are represented by playing with arbitrary color mappings, until the author finds a combination that shows something "interesting", which is also hopefully something that they were looking for....

I suspect that it is a rare image that receives the benefit of artistic creative inspiration.


Presenting 3-dimensional data is even more tricky!