Actually, the first author of the case report can't really promise to include someone as an author, if that person took photographs and little else. At least not if the author wants to be in compliance with the Vancouver rules, that are generally subscribed to by all major scientific journals.
"Authorship credit should be based on 1) substantial contributions to conception and design, or acquisition of data, or analysis and interpretation of data; 2) drafting the article or revising it critically for important intellectual content; and 3) final approval of the version to be published. Authors should meet conditions 1, 2, and 3."
Frankly, it's difficult to justify that taking photographs would satisfy any of the three requirements. At most, it would include 1), but not the other two conditions.
However, such assistance as mentioned by the OP CAN result in an acknowledgement:
"All contributors who do not meet the criteria for authorship should be listed in an acknowledgments section. Examples of those who might be acknowledged include a person who provided purely technical help, writing assistance, or a department chair who provided only general support. Editors should ask authors to disclose whether they had writing assistance and to identify the entity that paid for this assistance. Financial and material support should also be acknowledged."
http://www.icmje.org/#author
Yes, I do know that especially attendings and other senior staff often get co-authorship with little or no involvement in the study. However, the Vancouver rules are there for a reason, and personally I think it's just plain wrong that one should be able to claim co-authorship for a work contibution of "one hour" as some other posters have gotten away with.
Also, remember that you need to sign a release form (and hopefully read the manuscript) before you can become a co-author.
If any and all involved in a study gets a co-authorship, it will only further debase the value of publication authorship. So while it's difficult to resist the lure of authorship, please bear that in mind when demanding co-authorship for your contribution to studies. Personally, I have on several occations rejected contributions from people, who demanded co-authorship simply for supplying me with a few slides, or similar contributions.