Sony Alpha SLT-A37 Handbook page 26

Attaching a lens
• When storing, turn over the lens hood and place it onto the lens backwards.
Note on changing the lens
When changing the lens, if dust or debris gets inside the camera and
adheres to the surface of the image sensor (the part that acts as the film), it
may appear as dark spots on the image, depending on the shooting
environment.
The camera is equipped with an anti-dust function to prevent dust from
landing on the image sensor. However, quickly change the lens away from
dusty locations when attaching/removing a lens.
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