Dilip Krishnan and Rob Fergus at New York University have developed a dark or invisible flash which uses infrared and UV light to take photos in dark places without the nasty glare of a standard flash. Their dark flash camera is made by modifying a flashbulb so that it emits light over a wider range of frequencies and filters out the visible light, and removes filters that prevent the silicon image sensor from detecting IR and UV rays. This flash results in a crisp image which does not have correct color balance, and looks like night vision
photography. To correct the colors of the image, the camera also takes a quick color image sans flash right after the dark flash image. The image produced in this second image is predictably grainy and unclear, but the colors are correct. Software is then used to combine the information from the photos to produce the final image (an example of which you see above). There are some minor problems with the method -- objects that absorb UV light (such as freckles!) do not show up using this method. The pair will present their work at the Siggraph conference in New Orleans in August.