> If you take 3 sonsecutive photographs through a red, a blue and a
> green filter, the resulting pictures can be used to reproduce the original
> colours of the subject. Taht's the principle of colour separation as it's
> used in the offset procedure, for example.
>
> Now I wonder what happened if you took 2 or 3 X-Ray photographs
> through a same object, interposing successively 2 or 3 sheet of different
> opaque materials. Could these radiographs be used to elaborate a coloured
> picture, which would permit the optical distinction of different materials?
>
> Anybody has proved that? Is there some literature about it?
>
> And another question: If it does'nt work, why not?
The X-ray analogue to RBG separations would be to expose the X-ray
plates to 3 different X-ray wavelengths to get a false colour
composite image. This is what is commonly done with remote sensing,
which assigns infrared and UV bands to various colours in the final
print.
If you make three exposures through different partially opaque materials you
will end up with different exposures. When you assign colours
(arbitrarily?) to the different exposures you get what is commonly
called "posterization". This can be done starting from a single B&W
negative as well.
I don't think posterization will give you any additional information
over a single monochrome exposure that's been done well. I'm not an
X-ray expert so meyber there are some other effects that come into
play.
Sandor Mathe -- sandor.mathe@prior.ca
(905) 670-1225 x333
FAX (905) 670-1344