"Invisible Flash" Takes Photos in the Dark

Using a combination of infrared and ultraviolet light, a "dark flash" camera eliminates the garish effects of a regular flash.

Everyone hates flash bulbs--they make for crazy shadows, unflattering shiny spots, and distorted colors. But we deal with them because we don't have any good alternative, if we're looking to take pictures when it's dark out. Maybe not anymore: Dilip Krishnan and Rob Fergus at New York University have invented a "dark camera" whose unique flash doesn't have the familiar, telltale effects of normal bulbs.

The camera works using a flashbulb that emits a wider range of light--meaning IR and UV rays. Then, they had to tweak a camera sensor so that it detects those wavelengths. The major problem though was that this combination of hacks, on its own, would yield a weird image, much like that from a night-vision scope. So they programmed their camera to take a dual exposure--one brief, flash-free photo allows it to glean the right color information to correct the exposure. Here, for example, was a picture taken in the dark--which as you'll notice doesn't look at all like a picture taken with a flash (never mind that the photo settings make everything look a weeeeeee bit frightening):

dark photo

The one problem that remains is that some materials absorb UV and IR light, and thus don't appear in the post-flash images. One example: Freckles.

But there's clearly promise in the technology. The work will be presented in August's Siggraph conference in New Orleans.

[Via New Scientist]

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