By Hany Farid via Image Authentication and Forensics | Fourandsix Technologies
A video purportedly showing an eagle swooping down and snatching a baby has gone viral:
Given how unlikely the video seems, there is a vigorous debate about its authenticity. We performed a forensic lighting analysis on this video to determine if it is real or fake.
To perform this analysis, we connect points on an object with their corresponding cast shadow. Because of the geometry of cast shadows, all such constraints must intersect at a single point. (For an understanding of why this is so, read my previous blog post about shadows.)
Shown below are five such constraints from one frame of the video, just as the eagle is about to the grab the baby. The red lines are from the baby and eagle, and the blue lines are from the slide, adult, and stroller. You can clearly see that these shadows are not consistent with one another. The most likely scenario is that the baby and eagle are computer generated and were inserted into a real-world scene. Because this scene is outdoors and illuminated with a single light source (the sun), there is no physically plausible explanation for this inconsistency in shadows.
[click for a magnified view]
: Minutes after posting this blog entry, we discovered that the perpetrators of the hoax had come forward
. They managed to fool much of the internet pretty successfully, but it appears that they can still use some practice in refining their 3D simulations.]
By Hany Farid via Fourandsix Technologies
Ever since the assassination of President Kennedy, numerous theories have circulated claiming that Lee Harvey Oswald, the accused assassin, acted as part of a larger criminal conspiracy. It has been suggested, for example, that incriminating photographs of Oswald were manipulated and hence evidence of a broader plot. I have never been particularly interested in these conspiracy theories. I do, however, like that at least one aspect of the theory was testable – were the shadows in the Oswald backyard photo physically plausible or not?
A portion of the argument for photo tampering goes something like this. Consider the shadow cast from Oswald’s body onto the ground. The orientation and length of the shadow suggest that the sun is to Oswald’s left and relatively low on the horizon. The long straight shadow under Oswald’s nose, however, suggests that the sun is directly above him. These seemingly incongruous shadows have led to speculation that Oswald’s head was pasted into the scene. In fact, Oswald himself claimed that the photo was a fake and had been altered to falsely implicate him.
I thought that there was a chance that the photo was fake because it does seem at first glance that the shadows in this photo are inconsistent with one another. I also know, however, that our visual system can be spectacularly bad at judging such things as lighting and shadows in a photo.
In order to reason about the shadows in this scene we need a three dimensional model of the scene (Oswald’s head/body and the ground plane) and the three dimensional location of the sun. In general, determining three dimensional information from a single two dimensional image is an under-determined and difficult problem. Estimating three-dimensional models of a person’s head, however, is relatively easy because of the somewhat constrained and well understood geometry of human heads.
A frontal and profile view are required to build a 3-D model of a person’s head – Oswald’s mugshots were perfect for this.
Keep Reading: … Photo Forensics Software | Fourandsix Technologies – Blog – Lee Harvey Oswald.
Hany Farid via Fourandsix Technologies
Abraham Zapruder’s Bell & Howell Zoomatic movie camera, in the collection of the US National Archives (Photo credit: Wikipedia)
Over the years there has been a handful of images that many individuals, organizations, and media outlets have asked me to analyze. One of these is the so called Zapruder film which captured the assassination of President John F. Kennedy. Since its release, there has been much speculation as to the authenticity of this video. Here I will describe a forensic analysis applied to one aspect of the Zapruder film that, as with the Lee Harvey Oswald photo, debunks certain claims of manipulation. (WARNING: some of the images and descriptions are graphic.)
Abraham Zapruder captured the most complete documentation of the assassination of JFK. After its public release in 1975, challenges to the authenticity of the Zapruder film began to surface. The Zapruder film has been analyzed for evidence to support alternate theories of who and how many people were involved in the assassination. For example, it has been argued that on frame 317 (and neighboring frames) what appears to be a shadow on the back of JFK’s head is the result of tampering, purportedly to conceal evidence of a shot exiting through the rear of JFK’s head. This shot could only have come from a second shooter, as Oswald was positioned behind JFK.
Frame 317 of the Zapruder film (right: a magnified view of
JFK and the questioned shadow on the back side of his head.)
In order to determine if the lighting and shadows in this scene are physically plausible I constructed a 3-D model of the sun’s location and the relevant scene geometry.
JFK was assassinated on November 22nd, 1963 at 18:30 (UTC) in Dealey Plaza in Dallas, TX. It is an easy matter to determine the relative position of the light at this time and place. According to the National Oceanic and Atmospheric Administration solar calculator, the sun’s azimuth and elevation at this location and date was 181.91 and 37 degrees, respectively.
We next need to know the angle between people and objects in the scene and the sun. At the time of his assassination, JFK’s car was traveling on Elm St. … (keep reading): Photo Forensics Software | Fourandsix Technologies – Blog – The JFK Zapruder Film.