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Washington (CNN) He campaigned on the huge crowd sizes, but the turnout for the inauguration of President Donald Trump appears to be smaller than that of his predecessor as measured by side-by-side photos of the two events.

It's hard to gauge crowd sizes and the National Park Service, which oversees the National Mall, doesn't offer estimates of any sort.

But the side-by-side images of Friday's ceremony alongside the 2009 inauguration of President Barack Obama show a significantly smaller crowd on the National Mall for Trump than for Obama. There is empty ground exposed in the Trump photos. The same spots were almost entirely covered eight years ago, when estimates at the time suggested 1.8 million people attended the inauguration. The images above do not capture people who might have viewed from the west side of the Washington monument. And there are some differences. The grass on the mall is covered in white plastic for Trump's inauguration, but not for Obama's.

The photo of Trump's inauguration was taken from television during his speech — peak time for the crowd.

The photo of Obama's inauguration was taken by Getty and doesn't indicate the time, but Trump's should represent his largest audience.

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