Lighting and Optical Tools for Image Forensics

M.K. Johnson

Ph.D. dissertation, Dartmouth College



We present new forensic tools that are capable of detecting traces of tampering in digital images without the use of watermarks or specialized hardware.  These tools operate under the assumption that images contain natural properties from a variety of sources, including the world, the lens, and the sensor. These properties may be disturbed by digital tampering and by measuring them we can expose the forgery.  In this context, we present the following forensic tools: (1) illuminant direction, (2) specularity, (3) lighting environment, and (4) chromatic aberration. The common theme of these tools is that they exploit lighting or optical properties of images.  Although each tool is not applicable to every image, they add to a growing set of image forensic tools that together will complicate the process of making a convincing forgery.