Rob Fergus, Associate Professor at NewYork University, and Dilip Krishnan, a first-year student at the same institution, have developed a flashgun that emits invisible light. According to a report by the New Scientist, the “dark flash” actually works over a wider range of wavelengths than normal flashes, but visible light is filtered out. In order to use it with a digital camera, the camera’s IR cut filter has to be removed. The resulting image is, unsurprisingly, monochromatic, and resembles the view through a night-vision system. To address this issue, Fergus and Krishnan have come up with the idea of taking two exposures - one with the “dark flash” and one without it, by ambient light. The second one is captured at a fairly high shutter speed, and is underexposed for it, but contains valuable colour information. In other words, the shot with the “dark flash” delivers the necessary luminance information, whereas colour is derived from the exposure captured by ambient light. The main benefit over regular flash shots? Well, the “dark flash” does not disturb or dazzle the models, Krishnan claims. The technique also makes for glare-free photos that do not suffer from the annoying reflections you see in many photos taken with “normal” flash.

Website: Dilip Krishnan’s Dark Flash Page

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