Without intending to we stumbled upon a Tokihiro Sato "Photo Respiration" exhibit, which was in the gallery next door to the Robert Koch Gallery. Sato's photos use interesting technique: he sets the photo for very long exposure (~1 hour) and walks around the photo with a flash light, pen light, or mirror, which he shines back into the camera for varying effect. The long exposure also means that photos like the one below of Shibuya Crossing are nearly empty of people and cars -- only faint ghosts remain.

Sato also has an interesting presentation: the photos are mounted in front of a bed of lights that shines through the semi-transparent print, which emphasizes the points of light (similar to viewing the photos on a computer screen). Some of the photos remind me of japanime scenes were the little light spirits in the woods start gathering (missing a specific reference here, but possibly Princess Mononoke). My favorite image in particular is one where the dots of light are huddled around a massive tree -- unfortunately I can't find an image of it online.

I also couldn't find the exhibit page, but this page has a fairly good collection of Sato photos (some in the exhibit, some not). There is also a book available under the same title as the exhibition.