It is not uncommon to redact information from a document or image prior to making it publicly available. A name, date of birth, or account number in a document, or a face, license plate, or identifying street sign in an image may be redacted for reasons of privacy or national security. A common form of redaction is to place a black region over the information to be concealed. Under certain circumstances, however, the concealed information can be deciphered.
Welcome to the Fourandsix blog, where you’ll find tips on image forensics techniques and commentary on issues relevant to photo tampering and the responsible use of imaging tools.
In 2011, the Chinese government aired video footage of a new fighter jet purporting to shoot down another jet. Shortly after its release, several viewers noticed a suspicious similarity between the released video and a scene from the movie Top Gun. The side-by-side comparison shown below confirmed their suspicions.
A team of MIT scientists, led by Prof. Adelson and Dr. Johnson, have created an incredibly cool device for making extremely detailed and rapid surface measurements. Althought this is outside of the scope of image forensics, it does have some interesting applications to fingerprint and firearm forensics.
I’ve always thought that one of the best features of a legal system is the notion that a person is innocent until proven guilty. In such a system, a defendant in a criminal trial does not have to prove their innocence. Rather, the prosecution must prove guilt beyond a reasonable doubt.1 I would argue that photo forensic analysts should employ similar standards. We should start with the assumption that a photo is authentic and only conclude that it is fake when the preponderance of evidence excludes any other reasonable conclusion.
For a while, I was publishing a semi-regular feature in this blog entitled “Truthful Photo Editing,” in which I described how best to approach the editing features in tools like Photoshop so as to maintain the original truth of a photo. One of the recurring themes of those posts is that there are, unfortunately, few firm rules about what tools and techniques are acceptable in a truthful workflow. Almost any tool can be used both sparingly in ways that enhance and severely in ways that distort, and what level of truth must be maintained is dependent on context. The type of editing permissible in photojournalism differs from what is permissible in a legal setting or in a medical image. Ultimately there is no substitute for good judgment. But applying good judgment is hard, especially when the baseline of truth you’re comparing against is itself open to interpretation.