Sharon Lockhart’s two-part 93-minute record of a Maine clam-digger opens with a daunting gray expanse: empty slurry mudflats receding into an indistinct background, where land, sea, and sky blend. The view will clear up, the hour will change, tracks will zig-zag across the sand, but the shot’s position will remain constant. Similar in spirit to Lockhart’s 2003 farmer’s-progress hay-pile chronicle NO, Double Tide presents an even more resistant, almost obdurate portrait of work. The hazy middle-distance view of the digger with her basket draws attention away from the labor and toward the surfaces of Lockhart’s art: As she makes her bent-over way across the screen, the close-mic’d sound of clams slurped from the sand is the most vivid feature—a kind of magic-show extraction of goodies from within the image. (As the lone attendee at the press screening, I imagine critics previewing via DVD doing a lot of squinting and Windexing.) Part two, the color view to the first part’s near-monochrome, is more engaging, with the requisite rarefied variations on the setting’s visual and sonic detail: glistening mud, the remnants of a sunset, a pained “Oh!” from the subject. But for all the unvarnished coastal beauty and hypnotism in routine, there are stretches when the experience (of duration, of observation, of landscape art) can feel like, well, a bit of a chore.