@TechReport{Dartmouth:TR2009-656,
  author = {Eric Kee and Hany Farid},
  title = {{Detecting Photographic Composites of Famous People}},
  institution = {Dartmouth College, Computer Science},
  address = {Hanover, NH},
  number = {TR2009-656},
  year = {2010},
  month = {October},
  URL = {http://www.cs.dartmouth.edu/reports/TR2009-656.pdf},
  abstract = {
    Photos are commonly falsified by compositing two or more people into a single image. We describe how such composites can be detected by estimating a camera's intrinsic parameters. Differences in these parameters across the image are then used as evidence of tampering. Expanding on earlier work, this approach is more applicable to low-resolution images, but requires a reference image of each person in the photo as they are directly facing the camera. When considering composites of famous people, such a reference photo is easily obtained from an on-line image search.
  }
}