The judgment linked to by the article says:
During the period from 5 October 2007 to 11 April 2008, Mr Ryneš installed and used a [continuously recording] camera system
located under the eaves of his family home. The camera was installed
in a fixed position and could not turn; it recorded the entrance to
his home, the public footpath and the entrance to the house opposite. [my emphasis]
That is the context of the case.
He hadn't obtained consent from his neighbour to film the entrance to their home and therefore their family. He hadn't obtained consent from passers-by or warned them by means of a sign that there was a surveillance system monitoring that part of the public space.
The court ruled that:
The second indent of Article 3(2) of Directive 95/46/EC of the
European Parliament and of the Council of 24 October 1995 on the
protection of individuals with regard to the processing of personal
data and on the free movement of such data must be interpreted as
meaning that the operation of a camera system, as a result of which a
video recording of people is stored on a continuous recording device
such as a hard disk drive, installed by an individual on his family
home for the purposes of protecting the property, health and life of
the home owners, but which also monitors a public space, does not
amount to the processing of data in the course of a purely personal or
household activity, for the purposes of that provision. [my emphasis]
If you recorded or took photos of your family members enjoying walking through Trafalgar Square, a very busy public space, it's likely you could successfully claim it was a purely personal or household activity - if the authorities were at all bothered by it (which they are not).