Sony ILCA-99M2 - Manual (Page 392)

Turn off the product following the instructions on the screen. 3
Detach the lens. 4
Push the mirror lock lever (A) and open the mirror. 5
Use the blower to clean the image sensor surface and the surrounding area. 6
After you finish cleaning the image sensor, push down the mirror until it clicks.
Push down either side (B) of the mirror.
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