And one of the reasons why Germany has very strict rules on video surveillance.
Doorbell cameras are a good example: they can't be used if they can see the street, see the pathway to the house or are put in communal areas of multi-residence housing (i.e. can't be used if it can see the hallway outside a flat that non-visitors to the specific flat have to pass.
The same for surveillance cameras, they cannot record the pavement or road or public areas of the property (E.g. driveway), but you can use them in the back garden, where you would not expect members of the general public to be passing.
Drones are similarly restricted. They can't be flown over housing or business areas. They can't be flown in any built-up areas really. They can be flown at model aircraft aerodromes, open fields or woods. But you cannot film anyone without their permission.
If you want to use a drone in a built-up area (E.g. promotional film for a company, documentary or a feature film), you can apply for a filming permit, but you still need a release from anyone captured on film, before you can upload it to the Internet or otherwise distribute it.