Specular Highlights
Surrounding lights reflect in eyes to form small white dots called specular highlights. The shape, color and location of these highlights tell us quite a bit about the lighting.
In 2006 a photo editor contacted me about a picture of American Idol stars that was scheduled for publication in his magazine (above). The specular highlights were quite different (insets).
The highlight position indicates where the light source is located (above left). As the direction to the light source (yellow arrow) moves from left to right, so do the specular highlights.
The highlights in the American Idol picture are so inconsistent that visual inspection is enough to infer the photograph has been doctored. Many cases, however, require a mathematical analysis. To determine light position precisely requires taking into account the shape of the eye and the relative orientation between the eye, camera and light. The orientation matters because eyes are not perfect spheres: the clear covering of the iris, or cornea, protrudes, which we model in software as a sphere whose center is offset from the center of the whites of the eye, or sclera (above right).
Our algorithm calculates the orientation of a person’s eyes from the shape of the irises in the image. With this information and the position of the specular highlights, the program estimates the direction to the light. The image of the American Idol cast (above; directions depicted by red dots on green spheres) was very likely composed from at least three photographs.
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15 Comments
Add CommentPhotoshop pictures are cool. As technology makes it easier to doctor photos, detecting them gets harder. In the latest version of Photoshop you can actually change the lighting angle.
Reply | Report Abuse | Link to thisJT
http://www.Privacy-Center.net
This was a fascinating read. Keep it up - tell us more!
Reply | Report Abuse | Link to thisI saw the bicyclists in your June issue. I admit the photo had me fooled, the only tipoff was the young lady's overly developed legs and the too relaxed look on her face. I suppose someone has already thought of the rather clandestine act of putting someone were they weren't, then leaving the burden of proof to them to prove they weren't. Great article!
Reply | Report Abuse | Link to thisYou failed to point out the simplest and most obvious indicator: halination, the appearance of a halo around an object in a digital image. Halination frequently occurs when digital images are manipulated by identifying and/or sharpening edges, required for some cut and paste alterations. A good, if unresolved example, was the widely published photo of OJ in Bruno Magli loafers. The picture was taken with a film camera, not digital, yet a distinct halo was seen around OJ and his shoes.
Reply | Report Abuse | Link to thisHaving edited so many photos in my time, spoting edited photos has become easier but as one redfoxone mentioned new versions of photoshop and corel paintshop pro photo come out it becomes harder and harder to find the fakes. Your programs sound great and I would love to see them in action on more photos... especially during the election.
Reply | Report Abuse | Link to thislauraannq
http://biscuitq.blogspot.com
Your article "Digital Image Forensics" SA, June 2008, could have picked a better example than the clumsily altered photo of the cyclists. It doesn't need digital techniques to spot a number of errors, including the lighting inconsistencies discussed in the article. Her neck appears to be growing too far down and on the right hand side of the chest, and it's incorrectly aligned with the rotation of the shoulders. Her facial features seem too fine for the broad male shoulders and chest she has been grafted onto. Her hair seems remarkably composed for someone supposedly flying along a road, and everyone else seems to need to sport a brand of goggles of some kind, why should she be any different? And in the background the fire hydrant appears to have been photographed from ground level, inconsistent with the shoulder height viewpoint of the main view.
Reply | Report Abuse | Link to thisI think it's hard to identify such those faked picture even though to use some kind of so-call high-tech, because the computer graphics technology, people can use software to make fake. Such as, 3Dmax, maya or XSI etc. Those software can output a large unmber of picture as a sequence and finally put it together as a film. For example, "The day after tomorrow","Transformers" and so on. Those film are all relied on the computer graphics technology to make 'fake' and also to 'deceive' the audience. In addition, the HDRI(High dynamic range imaging ), This technology can be provided for faker to get some accurate light information from where he/she want to make fake whether or not any foul light condition.
Reply | Report Abuse | Link to thisFor instance http://forums.cgsociety.org/showthread.php?f=132&t=636028
This was a very ineresting article. I'll be looking more closely at photos. I do now, the news hypes things up way too much as it is.
Reply | Report Abuse | Link to thisThis was an interesting article. While many of the techniques were familiar to me, the section on digital fingerprints was new. There is a small editorial mistake, though. (38+42+40)/4 does not equal 38. The correct equation is (38+42+40+32)/4 = 38.
Reply | Report Abuse | Link to thisOmgg tha is defo real , how can you not belive that ?
Reply | Report Abuse | Link to thismell and teagn are cool (:
Reply | Report Abuse | Link to thisFascinating article. Eye opening info. Have you ever studied the (in)famous photo of Lee Harvey Oswald holding a rifle and a pistol using these techniques? What was the result? There are conflicting shadows in that photo.
Reply | Report Abuse | Link to thisive seen many shoops in my time and i know from the pixels that this image is a shoop
Reply | Report Abuse | Link to thisI am a student and my major is image forensics.Could you send me some source code about this!?
Reply | Report Abuse | Link to thisI need some source code about image forensics and thanks for your help!!!
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