How can I get pictures from Shotwell on the notebook to the desktop?

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http://askubuntu.com – My father has a desktop and a notebook. The desktop is way more powerful and has RAID set up, so he uses it for editing and storing his pictures. But he spends several months a year away from home. So he has a notebook for this. He imports the pictures into shotwell on his computer. He likes to organise his pictures on the notebook already, by creating and naming the right events, deleting pictures and sometimes editing a bit. When he is back home, he wants to get his pictures on the desktop, without losing the names of the events in shotwell. Sadly, one cannot merge two shotwell database (HowTos)