The 1970s was a decade of dramatic social and political upheaval: women’s rights, gay liberation, environmental activism, an energy crisis, crippling inflation, not to mention Watergate and the final chapter of the war in Vietnam. No surprise then, that it was also a period of robust photography. “The 70s Lens” at the National Gallery of Art revisits the decade with over 100 works by more than 80 artists. The exhibition shows how photographers used the radical energy around them to reinvent the documentary photo, bringing a new tonality and attitude to urgent stories of the day. —Isabella Carter