When a digital camera captures a photo, the camera creates each pixel using a charge-coupled device—a microchip that is made up of millions of capacitors that get electrical charges depending on how intense the lighting is in a certain spot. Each of these capacitors has a lens and a color filter that creates one single pixel from a mosaic made up of red, green and blue filters.
The colors and brightness levels that we can physically see in our digital pictures are created by a demosaicing software, which is custom built for every camera model due to each camera's individual specs and subtle differences. Because of this, a certain camera model will generate distinct pixels—and unique relationships between its neighboring pixels—which can pinpoint the exact make and model of the camera.
Knowing this information could greatly help forensics teams since each digital camera has a shelf life of about 18 months, which would significantly narrow the pool of where and when it was sold. Although it is not perfect, early tests have shown this technique has proven to be 90 percent accurate, which is still an A in my book! [New Scientist via Slashdot]
