Aperture Priority Mode - an undocumented feature
In addition to the "quirks" of the Landscape and Aperture Priority Modes (neither mode works as documented!)..... The camera also behaves differently in full Manual Mode (it changes the settings, whether you want it to or not to compensate for available light)...
At lower Zoom Levels, the camera will adjust the Shutter Speed Only, to try and compensate for available light...
For example: with the Camera preset to F5.6 Aperture, and 1/48 sec. shutter speed, the camera will adjust the shutter speed between a range of 1/30 to 1/291 sec, to try and "auto expose" the shot for lower or higher light levels, even though you're in manual mode.
At an Aperture Setting of 2.8 and 1/48 of a second, the number of internal steps in shutter speed the camera is willing to take, increases dramatially - for example: shutter speeds up to 1/600 of a second, even though you have the shutter set to 1/48 in manual mode.
The camera WILL NOT attempt to adjust the Aperture to compensate for proper exposure in available light (OR WILL IT??).... It depends on your Zoom settings! It won't if your're near to full wide angle, but IT WILL if you are using the Zoom.
Once you cross some unknown zoom threshold (it doesn't have to be at full zoom), then the camera begins to change both the Aperture and Shutter speed to compensate for available light, even though you are in "Full Manual", versus Auto Exposure Mode.
In Manual Mode, (as in Aperture Priority Mode), the amount of change the camera is willing to make to your settings, appears to be related to a preset number of internal steps, with the number of steps dependent on both Aperture and Zoom Settings, before it gives an EV Warning for Over or Under Exposure conditions....
The type (shutter speed only for wide angle, shutter and aperture for zoom) and amount (number of internal "steps" it takes to increase/decrease shutter speed and increase or decrease aperture), is dependent on the amount of zoom you are using for the current shot.