The A-series started as a budget line of cameras, although over time its feature set varied from low-end point-and-shoot cameras to high-end prosumer cameras capable of rivalling Canon's PowerShot G-series.
The series began with the A5, which was a very basic point-and-shoot camera line.
The Axx series that followed offered full manual control (on most models) in a fairly bulky body.
A-series cameras are generally powered by 2 AA batteries.
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