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Digital Photos Give Away a Camera's Make and Model
holy_calamity writes "Engineers at Polytechnic University Brooklyn have discovered that digital snaps shorn of any metadata still reveal the make and model of camera used to take them. It is possible to work backwards from the relationships of neighboring pixel values in a shot to identify the model-specific demosaicing algorithm that combines red, green, and blue pixels on the sensor into color image pixels. Forensics teams are already licking their chops."
So, if I shoot in raw mode, and then postprocess in software to get a jpeg, the demosaicing signature should merely identify the software, right?
Of course, I wouldn't be surprised to learn that the distortion uniquely identifies the lens used...
I better sell my Nikon D300. They'll be able to trace it back to me. Or one of the other gazillion people who also bought one. Hmm... on second thought...
"I'd rather be a lightning rod than a seismometer." -Ken Kesey
Feed your RAW images to photoshop, then hit NTSC color mode, then compress to jpeg. All their secret information is gone forever. Only idiots would let this work. and oh yea, those idiots didn't delete the Meta-Data anyway, cause they dont even know what it is.
So what if they can identify the make and model of camera. I own a D70. There are 300 billion d70 out there. Good luck on tracking a picture to my camera.
Its useful the same way knowing the car that raced away from the scene of the crime used a particular tire, with a particular wheelbase. Or that a bullet was fired from a particular make of gun.
Neither will positively identify anyone, but if you were already a 'person of interest' in a long list of people peripherally related to a case that detail might put you on a MUCH shorter list if it comes up that you have that model. Plus its useful when they are asking a judge for a warrant. Judges really like specificity with warrants... A "We want to search his home and car for a Canon Powershot X"; he blogged here about buying a Canon Powershot X, he was caught on this surveillance tape leaving the scene carrying an indistinct object, the dimensions and shape of which are consistent with a Powershot X, and we know the photos in question were taken with a Canon Powershot X"... that's got a lot more weight than... "We want to search this guy for a digital camera, because a witness said he owns a camera, and he was caught on tape holding an indistinct smallish object which could be a camera, oh... and the photos we're interested were taken with a camera."
A reasonable person would view the second as a complete fishing expedition, based on no evidence, practically everyone has a camera and he could have been holding anything on that tape. The first request is specific - the photos of interest were taken with that model, and there is reason to beleive the person HAS that particular model, and that he had it with him on the that tape. Sure it could be a coincidence, but a warrant for that particular camera if he has one to check it out, might not be unreasonable.
Its also not unlikely that they can pair photos to a particular camera if they have both on hand due to micro-scrathes and other unique lens defects... the same way they can pair laser pritners to printed output.