I think it's the case that they need clear conclusive proof of who was driving the car, and some cameras are probably crappy anyway.

Although I think for a lot of people if they were to pull up the driving licence of who the car's registered to, and masked-photo, it'd be pretty obvious - but I'm not sure how the law really works. Maybe for fleet-cars you might have some additional challenges.

Here's the article about it: https://yle.fi/uutiset/osasto/news/face_masks_fool_finlands_...

Edit: I'm British and the standard there is that the car is photographed from the rear and the owner has the legal liability to identify who was driving or face equivalent or worse sanctions. There seem to be both social and technical differences between the two (UK is almost exclusively radar based - and the evidence the police show must have the car crossing painted lines to show the speed. Some privacy concerns about who you might have been pictured in the car 'with'. In Finland they seem to be triggered by inductive coils in the road? I don't know, but I've never ever seen the painted lines)

The newer speed cameras in Finland, like pictured in the article use a tracking radar to detect speed. Older speed cameras (most cameras on the road still) use two induction coils built into the road.

In Germany, only the driver can get fined, not the car owner. However, if the latter cannot tell the authorities who was driving their car at the relevant point in time, they can be forced to start keeping a written log of who's driving their car at any point in time. That's only for the future though, it does not apply retroactively.