This survey of Pertti Kekarainen's photography from 1996 to the present is organized by series, from "Density" to "Tila." Kekarainen, a professor at the Academy of Fine Arts, Helsinki, is a key figure in the Helsinki School, and his goal is to represent invisible but persistent aspects of reality. He takes an unexpectedly old-fashioned direct route to a contemporary end, avoiding digital manipulation and using only mechanical capabilities of the camera to dot his images with colored spots like those you see after staring into a light. In the final image they appear as shadows and traces left not by the light but by the relationships of the people or objects near them, ghosts of ideas and conversations, akin to the ghosts in early spirit photography. Kekarainen has shown in Paris, Rome, Venice, Madrid and Tokyo, as well as all over Germany and northern Europe, where his work is widely held by museums.