Bright midday sun and a pitted concrete wall are poor ingredients for a dark, moody portrait, yet one small gridded flash can turn them into exactly that. Learning to shut out ambient light, shape a single source, and then finish the file with careful retouching gives you a look you can repeat almost anywhere with very little gear. With the camera set to shut out as much ambient light as possible before the flash fires, Glyn Dewis builds a one-light portrait outdoors in full sun. His settings land at f/16, ISO 125, and 1/250 s, and he stays within sync speed instead of turning to high-speed…