I would be a bit suspect of the reported identification on the photo in question. There is another photo of the same location with the camera backed up a bit that has two artillery guns sitting in the foreground. In this other photo, it has the men posing manning the guns. It is identified as "Confederate Artillery near Charleston, 1863". You can easily identify the same tree features as well as the same men found in both. The second photo is clearer and none of the jackets visible are trimmed.

http://www.old-picture.com/civil-war/Confederate-Charleston-artillery-near.htm

Frederick