Portfolio – All images cropped

Hi guys,
first of all: Thank you very much for an awesome theme like this. For free! I really enjoy it.

I have a problem with the Portfolio at my website http://www.l-schmuck.net/fotoimpressionen-2/
As you can see, I added several pictures. Nevertheless I cannot figure out why all my pictures have the same height & width. How and where can I change the settings, so that vertical pictures are shown as the Kitten in the example? http://demo.onedesigns.com/pinboard/?page_id=32

Thank you very much in advance
Best regards from Norway