Paintings can talk, but not photos?

[redlena2004]

No: HPFGUIDX 110660

Hello.  I've just joined HPforGrownups because of something 
that suddenly struck me as odd when I was re-reading Order of 
the Phoenix.

Has anyone ever heard an explanation why the paintings in 
Hogwarts can not only move but also talk while photographs, like 
those in the photo album that Hagrid had given Harry of his 
family, only move?

There are various examples of people talking with the subjects 
of paintings... the fat lady in the Gryffindor tower entrance 
painting, the knight (Sir Cadogan, wasn't his name?) who was 
the replacement for the fat lady when her portrait had been torn, 
and of course, all of the former Hogwarts headmasters in their 
portraits in Dumbledore's office.  But there are no mentions, that 
I can recall, of anyone ever talking to the subject of a photograph.  
And I'm sure Harry would have talked to his parents' photos if he 
could.

I just wondered whether anyone was familiar with a rationale for 
this, or whether it was just one of those peculiarities that suit the 
plotting?

Thanks!
-- redlena2004