The just-announced Galaxy S9 pretty much looks the same as last year's Galaxy S8. But that's okay. The Galaxy S8 itself was a pretty radical departure from the S7 before it, featuring really tiny bezels and a gorgeous Infinity Display.

So, how does it differ from last year's model? Easy: variable aperture.

Samsung Galaxy S9 Gets 'Revolutionary' Camera

Samsung calls the rear shooter on both the Galaxy S9 and S9 Plus as "the revolutionary camera that adapts like a human eye." This feature has only ever appeared on one smartphone ever, and that was 2009's Nokia N86. It might seem new, but actually, this special camera mechanism has been around since the early days of film photography in the mid-1800s.

Variable aperture means that the aperture on the phone is able to change. In the case of the Galaxy S9 phones, those are f/1.5 and f/2.4. For perspective, the Galaxy S8 had a fixed aperture of f/1.7. A lower number means a wider aperture, and the wider it is, the more photos look brighter, even in low-light conditions. Having a variable aperture brings both phones a step closer to DSLRs, which are capable of using multiple apertures, not just two.

That's not to say that the Galaxy S9's camera is comparable to DSLRs. It's just that engineering tiny camera phones are extremely difficult, and one that changes apertures on the fly is an astonishing achievement.

How The Variable Aperture On Samsung Galaxy S9 Works

So, how does variable aperture work? First, think of the aperture as a human eye. When it's really bright out, a person might squint a little to see better. When it's really dark, it's the opposite. The Galaxy S9's camera automatically switches from its two apertures to give the best photo possible.

When shooting in low light, the phone will automatically switch to its f/1.5 setting, delivering brighter photos with less noise. When there's plenty of light source, however, it will shoot using the f/2.4 setting, giving correctly exposed photos, as the narrower aperture prevents excessive sunlight from overexposing the shot.

Variable aperture isn't the only astonishing thing about Samsung's new flagships. At f/1.5, the lens is also the widest aperture seen on a smartphone thus far, surpassing the LG V30's f/1.6 lens.

Combined with optical image stabilization, complex image processing, variable aperture could really put the Galaxy S9 at the forefront of smartphone photography. Time, however, will tell.