My NextGen Galleries are HUGE!

I really like this plugin. But I am scratching my head over why a gallery I created that consists entirely of 320×480 (portrait mode) images shows up as a 620×930 slideshow. I am using Image Browser. Equally odd, if I choose slideshow, they show up as even smaller images than the original. How do I get them to appear at the native dimensions? (I’ve tried blanking out the dimensions boxes in Gallery->Options->Images with no luck.) Thanks in advance!