In terms of design, Samsung definitely played it safe with the Galaxy S9. There’s no iPhone-esque notch, no zany new materials — there’s even a headphone jack, that’s how straight-laced Samsung went. But the Galaxy S9 is far from boring, and that’s mostly thanks to the camera.

The primary camera (there’s a secondary telephone lens as well) on the back of the Galaxy S9 has a physical dual aperture, a feature that we haven’t seen on a smartphone camera for over a decade. It adjusts from f/2.4 to f/1.5 depending on the lighting, something that lets the camera vary exposure of an image without messing with the shutter speed or ISO. Installing a variable aperture helps capture sharp images in daylight while also having industry-leading low-light performance, something that shone through in our review.

Of course, variable apertures are nothing new to the photography industry. The impressive thing is how Samsung managed to miniaturize the physical mechanism necessary for a variable aperture and put it in something the size of a fingernail. JerryRigEverything tore down the camera (and the entire phone) on YouTube, and I highly recommend watching the video to fully understand how the aperture works.

Surrounding the camera sensor is a mechanical aperture unlike anything I’ve ever seen. Unlike the iris-style aperture that DSLR or mirrorless camera owners are used to, the Galaxy S9’s camera has two plates, actuated by a lever, which slide across the camera to limit the available light. There’s no in-between setting: you get your pick of f/1.5 and f/2.4, but that’s it. You might expect some kind of clever electronic system in a smartphone, but it seems that Samsung simply installed a mechanical system with a lever, actuated by a servo, which presumably turns a shaft and pushes the plate. At the scale we’re talking about, that kind of engineering is simply incredible.