One of the greatest pleasures of street photography is the unexpected. I was walking through the ancient brick medina of Tozeur, photographing people as they passed back and forth through the distinctive arches that link one set of streets with another. I heard the roar of an approaching motorbike, pre-focused on the edge of an arched tunnel entrance, and shot a burst of images just as it was about to cross from light into darkness. One of my frames revealed a small child riding in front and smiling up at his father. I never noticed the smile as I shot, but it rewarded me as I studied the detail a moment later.