Tag Archives: Hany Farid

Image Authentication and Forensics – The Moon Landing Photos

By Hany Farid via Image Authentication and Forensics | Fourandsix Technologies

By some counts a surprising number of people believe that the 1969 moon landing was a hoax. These dis-believers point to, among other things, purported inconsistencies in some of the moon landing photos. I’ll describe the application of a new forensic technique that refutes some of these claims.

Shown below is the iconic photo of Buzz Aldrin in which the physical plausibility of the lighting and shadows has been called into question.

moonlanding

I have previously described how cast shadows in an image can be analyzed to determine if they are consistent with a single light source. In order to determine if shadows are authentic, we connect points on a shadow to their corresponding points on the object. These lines should all intersect at a single point (or in the special case, be parallel) — this point is the location of the light source projected into the image. The application of this forensic technique (as shown here) requires a clearly defined shadow to object pairing (e.g., the tip of a cone). Such shadows in the above photo are in short supply thus limiting the application of this forensic technique.

In collaboration with Dr. Eric Kee (Columbia University) and Prof. James O’Brien (UC Berkeley) we recently developed a new forensic technique that can be applied to ambiguously defined shadows [1]. In this analysis, we start at any point on a shadow and draw a wedge-shaped constraint that encompasses all parts of an object to which the shadow may correspond. Shown below is one such constraint. The constraint encompasses the entire sphere because there is no systematic way of reasoning about which part of the sphere is associated with a particular spot on the shadow.

moonlanding2

In the above figure, the shaded red region constrains the projected location of the light source. While obviously not as specific as a single line constraint, this approach allows us to analyze all cast shadows in an image.

Because we can now handle ambiguous shadow-object pairings, we can also exploit attached shadows to determine the location of the light source. An attached shadow occurs when an object occludes the light from itself (e.g., a non-full Moon). Shown below, for example, is an attached shadow on the sphere’s surface. The line that is tangent to an attached shadow constrains the projected location of the light source to be on the illuminated side of the object.

moonlanding3

Multiple cast and attached shadow constraints can be specified in an image. If the shadows are physically correct, then all of the constraints will share a common intersection (this consistency check is automatically determined using standard linear programming). Any violations of these constraints is evidence of photo tampering.

Shown below is the result of this new shadow analysis applied to the moon landing image. The cast shadow constraints are shown with solid red lines and the attached shadow constraints are shown with dashed lines. All of the constraints are consistent (the triangular region outlined in black denotes a common intersection). Despite some claims to the contrary, the lighting in this spectacular photo is physically consistent.

moonlanding_analysis

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[1] Eric Kee, James O’Brien and Hany Farid. Exposing Photo Manipulation with Inconsistent ShadowsACM Transactions on Graphics, 32(4):28:1-12, 2013.

[2] Eric Kee’s presentation at SIGGRAPH, 2013.


[END] via Image Authentication and Forensics | Fourandsix Technologies

The Baby-Snatching Eagle: Real or Fake?

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]

[UPDATE: 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.]

Photo Forensics: Is The Lee Harvey Oswald Photo A Fake?

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.

Photo Forensics: Is The JFK Zapruder Film Faked?

Hany Farid via Fourandsix Technologies

Abraham Zapruder's Bell & Howell Zoomatic movi...

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.

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