This article was taken from the February 2015 issue of WIRED magazine. Be the first to read WIRED's articles in print before they're posted online, and get your hands on loads of additional content by subscribing online.

All photographers rely on light for their work, but Nicolai Howalt is more interested in its capacity to heal. The Copenhagen-based artist's new series Light Break examines the history of phototherapy: specifically the work of 19th-century Faroese physician Niels Ryberg Finsen, who pioneered using light of different wavelengths to treat medical conditions including smallpox and lupus vulgaris. "Lupus vulgaris were skin legions -- they were pretty damaging and you couldn't treat it in any way," says 44-year-old Howalt. "So [Finsen] started using sunlight. He put his patients in front of lenses and used filters to leave out everything but ultraviolet beams." (Finsen won a Nobel Prize for his discovery in 1903.)

Working with the Copenhagen Medical Museum, Howalt gained access to Finsen's equipment and turned it to a more artistic purpose. By exposing 20cm x 25cm Fujifilm silver halide photographic paper to light using the physician's original crystal lenses, Howalt created photograms of the otherwise invisible spectrum -- the lenses produce halos of different-coloured light. "The silver is still reacting at these low 200- to 250-nanometre wavelengths," he says. "These lenses have never been used for photographs."

Howalt is now combining the series with Finsen's own photography and writing -- including the doctor's personal shots of his patients -- into a book, Phototherapy (due in the summer), with the Wellcome Trust. "It's very important for me that it's not just aesthetic," he says. "This is medical history."

Howalt's images will be exhibited at the Martin Asbaek Gallery in Copenhagen from January 1 to February 14

This article was originally published by WIRED UK