ARS Technica reports users can now use Google image search to find images that only contain faces:
For example, a general image search for "Ars Technica" produces a variety of image results, but when appending "&imgtype=face" to the end of the URL, all new results contain photos of people.
The hidden feature was discovered by Google Blogoscoped, and there is currently no way to indicate that you only want to search for faces through the image search interface. However, both "&imgtype=face" and "&imgtype=news" trigger different search results than what is presented by default—the latter showing only images that are associated with news stories.
The technology appears to be the fruit of Google's 2006 acquisition of Neven Vision, a company that had developed techniques for facial recognition in photos. "Neven Vision comes to Google with deep technology and expertise around automatically extracting information from a photo. It could be as simple as detecting whether or not a photo contains a person, or, one day, as complex as recognizing people, places, and objects," wrote Picasa product manager Adrian Graham on the Official Google Blog last August.