The E-Sylum:  Volume 7, Number 30, July 25, 2004, Article 19

SPOTTING DOCTORED PHOTOS

  Electronic images are wonderful for publishing information
  about numismatic items.  But have those photos of auction
  lots been doctored?  The New York Times this week
  published an article about how digital photo forgeries can
  be unmasked.

  "It used to be that you had a photograph, and that was the
  end of it - that was truth," said Hany Farid, an associate
  professor of computer science at Dartmouth College who
  is a leader in the field. "We're trying to bring some of that
  back. To put some measure of guarantee back in
  photography."

  Over the last three years, Professor Farid and his students
  have become experts at forgery, making hundreds of images
  that look authentic but have in fact been digitally tweaked.
  License plate numbers are changed. A single stool standing
  on a checkerboard floor is suddenly a pair of stools. Dents
  on a car are wiped away with a few mouse clicks.

  The skillful tampering disturbed the images in ways that the
  human eye could not detect. But Professor Farid says his
  algorithms can spot them and sound the alarm.

  For example, when two images are spliced together - like
  the picture of a shark attacking a helicopter that has
  circulated around the Internet in the past few years - one
  or both of the original pictures usually has to be shrunk,
  enlarged or rotated to make the pieces fit together. And
  those changes, no matter how artful, leave clues behind."

  "In the long run, however, any method for preventing fraud
  may eventually come up short, most researchers in the field
  acknowledge.

  "At the end of the day, the person doing the tampering has
  the easier job. And they'll win," Professor Farid said. "We
  can't stop tampering. We can simply make it harder."

  To read the full article, see: Full Story

  Wayne Homren, Editor

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