Roger Highfield, editor, New Scientist magazine
This ghostly apparition has been created with a camera obscura, the ancient ancestor of the modern camera. Here, a scene outside the room is projected through a pinhole in one wall and appears on the opposite wall, upside down, but with colour and perspective preserved.
The Greek philosopher Aristotle described the phenomenon in the 4th century BC and the camera became an essential tool for artists of the Renaissance - or so painter David Hockney argues. He claims artists projected images onto a flat surface, using the detail to guide their art, an idea hotly contested by art historians and physicists alike.
The camera obscura has also become an enduring object of fascination for Cuban-born photographer Abelardo Morell, whose 1991 image of the process itself, Light Bulb, appears below. Since then, Morell has worked out the best way to photograph the faint images, including this view of Central Park, Manhattan.
Working at the Advanced Light Source at the Lawrence Berkeley National Laboratory, California, and FLASH, the free-electron laser in Hamburg, Germany, a team led by Stefano Marchesini has used the pinhole effect to create X-ray holograms of microscopic objects. When more holes were required to brighten the dim images, the challenge became how to assemble the information from overlapping images, says Marchesini.
Enter the impressive-sounding, massively parallel Fourier-transform holography (Nature Photonics, DOI: 10.1038/nphoton.2008.154). With an electron beam Marchesini's team etched a 2-micrometre-square reproduction of Leonardo da Vinci's Vitruvian Man, and created holograms of the drawing and of the bacterium Spiroplasma milliferum. He hopes the technique will be a useful tool since the X-ray holograms it creates are among the brightest, sharpest images of microscopic objects ever.
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