Super Small Images

So I have a gallery that im using as a wordpress portfolio. when you click on the thumbnail the images pop up in a lightbox but theyre super small. Some images are more square and some are longer and more rectangular. The images that are more square are coming up fine, but the ones that are longer and bigger get shrunk down super small. The square images start out at around 1000 w x 800 h and the longer ones are about 1000 w and 1400 h. When I click on the thumbnails to make the image full sized the bigger images end up getting shrunk down much smaller then the smaller starting images. Please take a look here http://bit.ly/R0qsZe all of the images are smaller than I would like but the longer images get super shrunk. Not sure whats going on. Thanks.

http://wordpress.org/extend/plugins/nextgen-gallery/