The Lower Manhattan skyline has gone through some large-scale change in the past 15 years. The Twin Towers are gone, 1WTC is here, and there are plenty of new mega-condos like 8 Spruce Street and 35XV. A detailed glimpse of the skyline and its changes can be seen in these two images shot by photographer Peter Walker.

Walker took the first photo in 2001, using a medium format Hasselblad film camera from the observation deck of the Empire State Building. The photo is perfectly exposed and full of rich detail, and features the Twin Towers prominently. He returned to the observation deck in May to attempt the same shot with his high-resolution Leica digital camera, and the second photo is the result (sadly, not cropped similarly to the first). In a post published on Petapixel, Walker explained that his goal was to compare the image quality of two top of the line camera systems—one analog, and one digital. In doing so, he also made a high megapixel document of change in New York.

Walker ultimately deemed his digital photo superior over the more grainy 2001 film shot, but his piece on the experiment kicked off some (occasionally heated) debate on photography websites about the relative merits of the two technologies. "I stayed out of that debate. But, when it quietened down, I did add the comment that 'digital vs film' didn’t seem like an issue worth getting angry about," Walker told Gothamist in an email. "The most obvious difference between the 2001 image and the 2016 image was the missing Twin Towers. I proposed that if anything was worth getting emotional about, it was the story of those missing Towers and the change, not only to skyline, but to the lives of all New Yorkers."

See more of Walker's work on his website.