With the growing availability and acceptability of digital media in various domains, the risk of image tampering is ever increasing. This increases the need to identify such tampering for authentication of digital media in domains such as jurisdiction, copyright and identity management, content analysis etc. One of the important facts related to this field is that we need to have high confidence in the forgery detection algorithms and approaches. These techniques must be validated and accepted by scientific community based on standard scientific bases. The motivation of this book is to design physics based algorithms so that manipulations from digital images can be identified. In this book, best-in-class forgery detection techniques are suggested which use inconsistencies in the light source directions to detect image forgeries.