I don't want the website to downsize images so have it set to allow massive size images but:

If I post a large Image as a thumbnail near the top of a thread, when the image is enlarged in a lightbox the top of the image is cut off, you can scroll down to the bottom of the image but you cannot scroll to the top of the image (only to the top of the actual website)

Anyway to stop this happening? On other sites the top of the enlarged lightbox image is in line with the top of the website or is not governed by it?

Any help thanks.