When you go to see "Now It Is Dark," Mark Ruwedel's latest exhibition of photographs at Gallery Luisotti, try to sneak a peek in the gallery's backroom, where, just above the entry, hangs a work by Ruwedel that is not part of the show per se, but which informs one's experience of it. Mounted behind glass are two panoramic views, each composed of multiple black-and-white prints. One is a recent view of Robert Smithson's 1970 signature earthwork, Spiral Jetty. The other shows the site of the unrealized Smithson work Island of Broken Glass, which would have been completed just before the Jetty, had environmentalist protest and local politics not gotten in the way of dumping 100 tons of its namesake material on a rock island near Frazier Point, British Columbia. Though these seem, by cursory examination of imagery, far removed from the images that make up Ruwedel's show, they share with them the artist's abiding curiosity about the was, is and might-have-been of marks made, alterations undertaken and claims staked upon the land by humans and sometimes other of Earth's inhabitants — from cuts into hillsides left behind by no-longer-present railways, to architectural and infrastructural relics of the early atomic age, to fossilized dinosaur tracks. All shot in Southern California's high desert regions, the black-and-white photos in this exhibition break into three groups — views of variously decaying and/or unfinished homesteading structures and small houses, shots of abandoned houses taken at dusk and, more unfamiliar to those familiar with Ruwedel's oeuvre, a collection of small "artifact" photos chronicling objects, many of them intimate, left behind on the desert floor. As the images of the structures leave one pondering the possible stories behind them, so too do the artifacts, while adding a layer of strangeness and wonder as to what people will leave behind in moments of abandon and abandoning. A hard conceptualist, with what seems at times an almost clinical, mug-shot-ish or crime-scene-esque approach, Ruwedel almost veils the heavy formalist that is also part of his being, and with which the conceptualist in him negotiates and sometimes yields. Key to this work, all shot with a 4X5-view camera, is a staggering degree of attention and care, which may sound sentimental given the potential nostalgia the sites and relics might evoke, but the attention is to detail, and the care is for the photographer's craft and the artist's project. There's a level of commitment in this work, telegraphed as utterly essential to the perfection of (imperfect) form and the crystallization of concept, that is present down to the last grain of the photo and the ever-present sand. Speaking of grains, Ruwedel is my colleague. We teach together, so you might take these comments with a grain of salt, but just go see the show, and you'll see for yourself.Gallery Luisotti: 2525 Michigan Ave., A2 (Bergamot Station), Santa Monica; Tues.-Fri., 10:30-6 p.m., Sat., 11-6 p.m., through July 17. (310) 453-0043, galleryluisotti.com.