For a medium that seems to prize veracity, photography has an awfully long history of tolerating—even encouraging—manipulation. The National Gallery of Art’s exhibition, “Faking It: Manipulated Photography Before Photoshop,” selects some of photography’s finest trickery, taking us from Gustave Le Gray’s famous compound sea-and-sky images to whimsical 19th-century stereoscopes purporting to show supernatural creatures, and from the manipulated “documentation” of Yves Klein’s performance-art project “Leap into the Void” to Jerry Uelsmann’s trippy visual concoctions. The images’ intentions vary— entertainment, commerce, news—but politics seems to be a particularly fruitful source of photographic prevarication: A chilling series shows the step-by-step elimination, over a 23-year period, of communist figures from a group portrait with Stalin. But the exhibit suggests that photographic fakery can be an effective form of political satire, demonstrated by the odd, elongated caricatures of 1920s Chicago Mayor “Big Bill” Thompson and Weegee’s 1968 portrayal of President Lyndon Johnson as Pinocchio.