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With their metallic sheen and intense detail, daguerreotypes usually offer viewers compelling visuals. But the images in the National Portrait Gallery’s exhibit “Double Take: Daguerreian Portrait Pairs” is uncharacteristically run-of-the-mill.

The exhibit consists of seven pairs of images of famous personages from the 1840s and early 1850s—the peak of daguerreian photography. The images in the exhibit are small in size, and the light is kept low due to preservation concerns. But while such difficult conditions are inevitable given the medium, they don’t do much to highlight the technique’s best face.

The exhibit’s thematic thread is promising—the notion that different daguerreotypists can produce notably divergent styles of imagery. In several pairs, though, the divergence between images is unremarkable. For instance, Jenny Lind, a famed soprano, is seen in images that are small and murky, while Daniel Webster’s pair is pocked by imperfections.

Other examples fit the theme more fully. It’s easy to see why John Quincy Adams liked the image that gave him an close-up, for instance. And the pair of Zachary Taylor images are divided between a small, muddy, vintage copy and a larger, more brightly lit example.

Among the pairs, the clearest contrast may be in the depictions of government official and scholar George Bancroft (pictured). The more impressive of the two has been hand-tinted, with a striking blue, cloud-sprinkled sky that contrasts well with Bancroft’s refined features and sharp tailoring. For once, the star isn’t the daguerreotype itself, but rather what was done in post-production.

Through June 4, 2017 at the National Portrait Gallery, 8th and F Streets NW. 11:30 a.m.-7 p.m. daily. Free. (202) 633-8300.