Portsmouth Harbor Light, off Portsmouth, New Hampshire, in the entrance to the Piscataqua River near the little town of New Castle

In 2015, documentary photographer Carol Highsmith received a letter from Getty Images accusing her of copyright infringement for featuring one of her own photographs on her own website. It demanded payment of $120. This was how Highsmith came to learn that stock photo agencies Getty and Alamy had been sending similar threat letters and charging fees to users of her images, which she had donated to the Library of Congress for use by the general public at no charge. In 2016, Highsmith has filed a $1 billion copyright infringement suit against both Alamy and Getty stating “gross misuse” of 18,755 of her photographs. “The defendants [Getty Images] have apparently misappropriated Ms. Highsmith’s generous gift to the American people,” the complaint reads. “[They] are not only unlawfully charging licensing fees … but are falsely and fraudulently holding themselves out as the exclusive copyright owner.” According to the lawsuit, Getty and Alamy, on their websites, have been selling licenses for thousands of Highsmith’s photographs, many without her name attached to them and stamped with “false watermarks.” (more: http://hyperallergic.com/314079/photographer-files-1-billion-suit-against-getty-for-licensing-her-public-domain-images/)

The collection/dataset uses media from the world's largest public domain source Picryl.com. It is made in two steps - first manually picked, and then, found semi-automatically, with aid of image recognition, it comprises of more than 5,000 images. Everything in the collection is in the public domain, so there is no limitation on the dataset usage - educational, scientific, or commercial.