I forget what the default is but the following, located in the index.php, will resize your images.
if ( $width < "440" ) { $new_width = "200"; $theClass = "eachpost"; }
else if ( $width < "660" ) { $new_width = "440"; $theClass = "eachpost"; }
else { $new_width = "660"; $theClass = "eachpost"; }
You can see that is says if your image is less than 440 resize it to 200. If it is less than 660 it will resize to 440. Anything over 660 drops to 660.