American Psychological Association or APA style is primarily used for research papers in the science and social science fields. Photographs used within research papers using the APA style must be cited on the reference page. How your citation is formatted depends on the origin of the photograph or image you're using. You need to determine where it came from -- such as an online website, library, journal, magazine, or any other published body of work -- who or what organization took the photo, the medium and the date it was taken.
If there are multiple images in the paper, you will start by writing under the image the figure number, like "Figure 1," in italics followed by a period. Then you will write the last name of the person who took or created the image, followed by the date it was created in parenthesis, followed by a period. Then write the word "Note" in italics followed by a colon and then where the image came from. If the image is copyrighted, say so and write who holds the copyright. Then list the year, followed by a period. If the photo was reprinted with permission, write that as well followed by a final period.
Papers written in APA style have References page, where citation are listed for all sources used in the paper. The photographer's or creator's name comes first in this citation, first name followed by last name, with no commas, then a period. After that, write the year in which the photograph was taken and a period. If you do not know the published date write "n.d." for no date. The title of the image follows, in italics, and if you do not know the title of the photo write a description of the photograph in brackets with a period outside of the close bracket. The medium of the photo then goes in brackets with a period outside of the close bracket. Lastly, you will write "Retrieved from ..." and then the source URL, without a period at the end. If the photograph did not come from a website, use the city and state abbreviation for where it was taken.