Cleaning The Image Sensor - Sony a9 II Help Manual

Cleaning the image sensor

If dust or debris gets inside the camera and adheres to the surface of
the image sensor (the part that converts the light to an electric signal),
it may appear as dark spots on the image, depending on the shooting
environment. If this happens, follow the steps below to clean the image
sensor.
1
Confirm that the battery has been charged sufficiently.
2
MENU 
The image sensor vibrates a little to shake off the dust.
3
Turn off the product following the instructions on the screen.
4
Detach the lens.
5
Use the blower to clean the
image sensor surface and the
surrounding area.
6
Attach the lens.
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(Setup)  [Cleaning Mode]  [Enter].