Cropped images

Hi,
I’ve just discovered that photos larger than a certain size get cropped in the single view. While a 675×900 is normally presented, a 900×675 gets cropped in a central banner, but a 720×481, for example, would still be shown in original size.
I couldn’t find a way to work on or prevent this and it seems not to depend on the WP Media thumbnail sizes, since I set the larger to 4096×4096 to be sure.
If there’s not a workaround to always show real size photos, could you at least tell me which is the maximum size allowed before cropping?
Thanks. 🙂

http://ww.wp.xz.cn/extend/plugins/gallery-plugin/