Chris McCaw, Heliograph #7 2012. San Francisco Bay, from Candlestick Point. Gelatin-silver paper negative.
This photograph features three exposures made over 3/4 of a day and thus shows not the sun but rather its path. Ken Johnson writes about the work in the New York Times:
"Instead of conventional film [McCaw] uses sheets of photo paper ordinarily used for printing positive images from negatives. In exposures of 15 minutes to 24 hours the lens concentrates the heat of the sun into a small, inflammatory dot. As the sun travels across the sky, the hot spot moves across the photo paper burning brown lines and cutting through the surface like a welder's torch slicing through steel."