Invisible flash takes photos without the glare

Although the dark flash gives a crisp image without disturbing those in the picture, the results have an odd colour balance that looks like a view through a night-vision scope.

To give the pictures more normal hues, Krishnan and Fergus used colour information from a brief, flash-free photograph of the same scene taken quickly after the dark flash image.

The second image is dim and blurry, and so it lacks some of the fine detail of its dark flash twin. However, the researchers use software to combine the sharp detail from the first image with the natural colours from the second image, resulting in a remarkably natural end result.