The complete photo is at the Library of Congress Online, and is part of their Civil War Photograph collection.
PHOTOGRAPHER Gardner, Alexander (1821-1882)
CREATED/PUBLISHED 1862 September.
MEDIUM 1 negative : glass, wet collodion.
REPOSITORY Library of Congress Prints and Photographs Division Washington, D.C. 20540 USA
CALL NUMBER LC-B815- 0588
REPRODUCTION NUMBER LC-DIG-cwpb-00255 DLC (b&w copy scan)
LC-B8171-0588 DLC (b&w film neg.)
COLLECTION Selected Civil War photographs, 1861-1865 (Library of Congress)
DIGITAL ID (b&w copy scan) cwpb 00255 http://hdl.loc.gov/loc.pnp/cwpb.00255
(intermediary roll film) cwp 4a39532
NOTES Civil War photographs, 1861-1865 compiled by Hirst D. Milhollen and Donald H. Mugridge, Washington, D.C. Library of Congress, 1977. No. 0131.
Photograph from the main eastern theater of the war, Battle of Antietam, September-October 1862.