I removed a lens from a large-format camera, detached its aperture, and set it on my westerly windowsill. The original camera obscura, centuries before, was not much more complicated than this. While my naked aperture rested there, like a retinaless eye, I photographed with another camera the light that bent through it, varying the lens's focal length. As my focus shifted from foreground to background, the aperture seemed to respond by thinning until it almost disappeared.