Hi X-rays are fuzzy because they are shadow graphs as x-rays cannot be focussed. I believe astronomers have x-ray telescopes that do focus the rays in a reflection mirror using grazing angle incidence. The x-ray tomography which I played a part in developing is a multiple exposure from different angles and the resulting shadow graphs are integrated to give a 3D image with a computer that takes the density of the image at various places and works out with the ray path and sums the contributions from different rays to map the hidden object as a synthesised 3-d image. I worked with a radiographer and a doctor in the medical school of St Bartholomew's hospital, London back in 1973. I worked out the general idea based on existing practise and worked out the mathematics which we put on a computer and then we did another computer algorithm that was able to change the number of cells and angles. The first ones were made by Marconi but they sold out to the American giant General Electric as the machine was very expensive who later sold out to a Japanese electronics company who improved it and it became now cheap enough for nearly all western hospitals. We later worked on Atomic magnetic resonance imaging that used a magnetic gradient and radio frequency resonance. With this the cell only resonates if the magnetic field and the radio frequency are exactly right for the atoms concerned and then only if the atomic microenvironment is correct. The system acts on electrons in a magnetic field where the resonant frequency depends on the local magnetic field. This is the result of the external field and the local field generated by the chemical environment. The system can show a map of chemical species in the body. Another system uses neutron magnetic resonance NMR, another uses proton magnetic resonance and that maps water. Since the body is nearly all water this magnetic resonance imaging method shows a map of all the tissue in the body as shades a grey (can be given false colours) except blood because blood is moving so blood vessels show black as empty. Not photography (Painting with light) but the general case of imaging. I don't think any one has done any artistic work with magnetic resonance. These are unseen colours.... Chris -----Original Message----- From: owner-photoforum@xxxxxxxxxxxxxxxxxx [mailto:owner-photoforum@xxxxxxxxxxxxxxxxxx] On Behalf Of David Dyer-Bennet Sent: 07 November 2009 16:40 To: List for Photo/Imaging Educators - Professionals - Students Subject: Re: Imaginary colors Speculation PhotoRoy6@xxxxxxx wrote: > There are no other colors except for the ones we see. The other part > of electromagnetic spectrum are just wave lengths. Any other animal > that can sense the other parts of the spectrum can only see them in > colors we know to exist but most probably sense them in different way > altogether. When we develop x-ray film it is black and white(i.e. > clear) and fuzzy. Your first two sentences may be tautologically true (if you're asserting that "color" is a human construct), but it's also useless. The third sentence is a matter of opinion, not fact; you can't know very much about the subjective experience of other species, and what we might know is fairly speculative. I do like the tests that show that pigeons, at least, see light frequency the way we hear notes (that is, ratios of frequencies mean something to them), though, and that would certainly qualify as "in different ways altogether". I don't think the point about x-ray film really establishes anything either. Remember, ordinary color film is really just B&W too, we use filters and dyes to make it look colored to us. And the "fuzzy" bit implies that x-rays are somehow fuzzy, whereas actually they're more precise than visible light (which is why they use UV and higher frequencies for lithography in chip fabs these days). -- David Dyer-Bennet, dd-b@xxxxxxxx; http://dd-b.net/ Snapshots: http://dd-b.net/dd-b/SnapshotAlbum/data/ Photos: http://dd-b.net/photography/gallery/ Dragaera: http://dragaera.info
