Last updated: August 2026
The S9 had something no phone has really attempted since: a mechanical variable aperture. The lens physically switched between two openings depending on the light. It is worth understanding, because aperture explains most of what separates a good phone camera from a poor one.
What aperture is
The aperture is the opening that lets light reach the sensor, written as an f-number. A smaller f-number means a wider opening and more light.
- Wide aperture — more light, better in the dark, shallower depth of field
- Narrow aperture — less light, but sharper across the frame in bright conditions
Almost every phone has a fixed aperture and compensates in software. The S9 changed it physically — wide at night, narrower in daylight.
Why the idea was abandoned
It worked, but computational photography overtook it. Modern phones combine several exposures in software and achieve more than a moving iris could, without the mechanical complexity or the failure point.
It is a recurring pattern in phones: clever hardware solutions get replaced by software ones. The same happened to the pop-up cameras.
See the Galaxy A80’s rotating camera.
What to take from it when buying
When comparing phone cameras, aperture and sensor size tell you more than megapixel counts. But the processing matters most of all — which is why sample photos beat specifications every time.
See why megapixels mislead and what pixel binning does.
Where the S9 stands now
From 2018 and past software support. Do not buy or finance one. If you own one, keep no banking apps on it.
See Galaxy S9+, Galaxy S8, Galaxy S10e, Galaxy S range and camera contract deals.
Frequently asked questions
What is aperture?
The lens opening. A smaller f-number lets in more light.
Why did variable aperture disappear?
Computational photography achieved more without moving parts.
Is the S9 worth buying?
No. It is past software support.
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This is general information, not financial advice.