It’s the work of a photographer called Andy Martin, who specialises in a photographic technique called the wet collodion process from the 19th Century. He has been using it to take photographs of the Northern Sinfonia, and presumably Wendy, also based at the Sage, had a go too. The reason for the project is described, with a gallery, and some explanations about the process, here.
The process brutally chisels out the features in high contrast under harsh lighting, all the while with the neck held supported to allow time for the exposure to be completed. The results are maybe not flattering in a conventional sense, every bump and wrinkle stands out like moon rock under the harsh glare of the sun, but the depth of character revealed is astonishing.