Deciphering old and tarnished photographs may soon be easier thanks to an imaging technique developed at the Canadian Light Source at the University of Saskatchewan. Professor T.K. Sham from Western University says using a tunable X-ray beamline at the CLS, he was able to reconstruct several daguerreotypes, the earliest known form of photographs.

Sham explains that old photographs contain something called image particles, which are made of mercury. “The experiment that we do at CLS uses a tunable X-ray source to target mercury, because X-rays penetrate much deeper into the image particles.” He says no matter how tarnished an old image may be, the optical reflectivity of the metallic image particles is what determine how well the image can been seen. “The denser areas give you the bright tone and the area that has less image particles will give you the dark tone.”

Because the X-ray beamline at CLS is tunable to whatever element or material you wish, Sham says this technique can be used in other applications as well, such as looking at bodily tissues.