You really don't need much "legalese" I suggest you go to the copyright office's website and read their circular on works made for hire." The basic language you need is "Photographer understands and agrees that all photographs, negatives, prints and other works taken, made or produced by photographer under this agreement are "works for hire" and that therefore all copyright rests with "Gimby" and not with photographer. Photographer agrees that if for some reason a court holds that the works are not "works for hire" then photographer hereby assigns all copyright in the works (including moral rights) to "Gimby." Photographer agrees to execute all such other and further documents as shall be deemed necessary by Gimby in order to effectuate the transfer of copyrights from photographer to Gimby." Here is a link to a form
http://www.docracy.com/4834/work-for-hire-agreement