A new study shows that the “pupil of the eye in a photograph of a face can be mined for hidden information, such as reflected faces of the photographer and bystanders.” What this could mean for law enforcement:
The researchers say that in crimes in which the victims are photographed, such as hostage taking or child sex abuse, reflections in the eyes of the photographic subject could help to identify perpetrators. Images of people retrieved from cameras seized as evidence during criminal investigations could be used to piece together networks of associates or to link individuals to particular locations. By zooming in on high-resolution passport-style photographs, Jenkins and co-researcher Christie Kerr of the School of Psychology, University of Glasgow were able to recover bystander images that could be identified accurately by observers, despite their low resolution.
Megan Garber explains how it’s done:
First, you have to zoom in (really, really zoom in) on images of eyes—since, as Jenkins notes, “a face image that is recovered from a reflection in the subject’s eye is about 30,000 times smaller than the subject’s face.” Then you have to enhance those zoom-ins to isolate the faces—the “bystander images“—that the human subjects’ pupils contain. But even if you do that, the question remains: Are the pupil-mirrored images, given their small size and curvature, even discernible as faces? If the reflection in the eyes is someone other than yourself, can you make out who it is?
To test that, the researchers presented a series of pixellated faces—an average of only 322 pixels each—as part of a face-matching task they administered to subjects. The subjects who were unfamiliar with the bystanders’ faces were able to match the pixellated faces to the standard images of them with 71 percent accuracy; when they were familiar with the faces (if the pixellated face belonged to, say, Barack Obama), they performed with 84 percent accuracy.
(Hat tip: Kottke)