Gone in a flash.SEEHelios: Eadweard Muybridge in a Time of ChangeWhat: The first retrospective of the granddaddy of photography’s work showcases more than 300 objects (proofs, glass negatives, camera equipment).Why: Check out the trippy zoopraxiscope projector from 1879.When: Sat.-July 18. Wed. & Fri.-Sun., 10 a.m.-5 p.m.; Thurs., 10 a.m.-9 p.m.Where: Corcoran Gallery of Art, 500 17th St. NW, at New York Ave. (202-639-1700). Admission is free on Sun. (reg. $10).HEARDone&Done FestivalWhat: Twelve bands from D.C. and NYC play the all-day show before they do it in the Big Apple the following week.Why: Ra Ra Rasputin, Loose Lips, and The Subjects.When: Sat. Concert, 2-11 p.m.; after-party, 11 p.m.-3 a.m.Where: Concert, All Souls Unitarian Church, 2835 16th St. NW, at Harvard St. Tickets ($12) at the door. After-party, Velvet Lounge, 915 U St. NW, b/t 9th & 10th Sts. (202-462-3213).EATCornercopia SandwichesWhat: The pint-size market sells six signature sammies ($6-$9) like The Stadium (cracked pepper turkey, avocado, bacon, and a spicy house sauce).Why: Local organic ice cream, baked goods, beer, wine, and other pantry necessities.When: Mon.-Fri., 8 a.m.-9 p.m.; Sun., 10 a.m.-6 p.m.Where: 1000 3rd St. SE, at K St. (202-525-1653).FETEBenning Library OpeningWhat: Celebrate the new ecofriendly establishment with music and dance performances by the Washington National Opera, Beat Ya Feet Kings, and others.Why: Board games, spoken word, and personal storytelling.When: Sat., 10 a.m.-4 p.m.Where: 3935 Benning Rd. NE, at Minnesota Ave. (202-281-2853). Admission is free.Photo: Eadweard Muybridge, Leland Stanford Jr. on His Pony “Gypsy” — Phases of a Stride by a Pony While Cantering, 1879 / Collodion positive on glass / Courtesy of the Corcoran Gallery of Art, Washington, D.C.