X-rays

X-rays

You know those annoying people who always have to go one better? You’ve just bought a secondhand 85mm f/1.4 lens, and they have found their ‘good old f/1.2 – no Bokeh like it. Don’t get that with a Sigma!’

Well, if you have a camera converted for shooting in the UV area of the spectrum, they are going to get out the kit for doing x-ray images. ‘Penetrates haze, wood, flesh. Only stops at the bones!’

Technically, x-rays are the part of the spectrum beyond UV, with a wavelength four orders of magnitude less than visible light. We’re talking very short wavelengths indeed, where millimetres give way to microns and eventually to angstroms or Å. At the opposite end of the spectrum (quite literally) heat has a wavelength around a millimetre, radar begins around 10mm, and radio waves are measured in metres (remember the BBC Light Programme at 1500 metres?)

Wilhelm Röntgen discovered and named x-rays (X for unknown), though colleagues wanted to name them after him. In some languages, the colleagues got their way – when my wife fractured her ankle on holiday in Greece, the first doctor to treat her, at a cottage hospital in Archangelos on Rhodes, said that a full diagnosis would require a ‘Röntgen’ – technology he didn’t have available.

X-rays are problematical to work with: think how the dentist retreats when taking an image of your teeth. Small doses are pretty harmless, but long or repeated exposure is harmful. The very high energy of x-rays damages tissue, and may result in burns in the short term, with cancer as the long-term risk.

But the benefit of identifying a medical problem with a small exposure to x-rays massively outweighs the risk, and makes fractures, cancers and various other problems identifiable, quantifiable, and therefore, usually, treatable.

X-rays are also employed in security scanners (which don’t, these days, cause problems with film in your luggage at the airport), and ‘hard’ x-rays, with the shortest wavelengths, are used in industry to check components for faults and fractures.

It’s no wonder, given that the rays are difficult and potentially dangerous to work with, that there are few purely photographic applications – but just occasionally, they can bring out the perfections of nature, rather than the imperfections that arise in a man-made world. And the results are utterly beautiful.