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."

Comments

stretch?

[Speare]

As even the cellphones are producing 3 megapixel images now, very few people need to be passing full-resolution originals around. If you scale the image down to a screen-usable 1 megapixel image, there's not going to be a lot of bayer mosaicking information still available.

What about multiple cameras using the same sensor?

[Chirs]

Quite often there are different manufacturers using the same sensor. Since this locks in the physical aspects of the sensor layout, I would expect the demosaicing algorithm to be basically identical across all these bodies.

Even after image manipulation?

[MR.Mic]

I wonder if this method still holds up after noise removal, or even something as simple as an image size reduction. Anyone more knowledgeable on the subject care to speak up?

Re:Even after image manipulation?

[morgan_greywolf]

I doubt it. I do a LOT of image processing, and I have to say that after color correction, noise removal, etc., I very much doubt that this technique would hold up.

Re:What about multiple cameras using the same sens

[fugu]

After the sensor takes the RAW data, the camera processes the image (some noise reduction, curves, and compression) to get a jpg. Since this conversion would vary between manufacturers (or even RAW software) I'd imagine that the process would leave behind similar "fingerprints."

Re:So What?

[xIcemanx]

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.

RTFA:

While many people own the same camera models, Pollitt believes that this technique can still be used forensically. He says that because digital cameras have a shelf life of only 18 months, this can help to narrow down when and where it was sold. Just because it won't immediately narrow it down to a single suspect with perfect accuracy doesn't mean it won't be helpful in investigations.

Re:So What?

[Anonymous Coward]

The bad guys on CSI, and their smug, latte drinking lawyers. Always demanding warrants and to be released if they aren't being charged with anything! EVIL

The only EVIL on CSI shows is the way the motherfucking cops use extortion.

"You don't want to give up privileged information on this guy? Fine, we'll be back with a warrant. Of course, we may have to dismantle your office for a couple of weeks to do a thorough search. What does a couple of weeks mean to your business? You do understand, don't you, that when we seize (God, how those bastards love the word "seize") your computer, our clumsy techs might return it with some important files no longer readable? So sorry. ... Oh, yes, ma'am, that's the perp we were inquiring about. Thank you for your cooperation."

Re:Raw images?

[Facegarden]

...Of course, I wouldn't be surprised to learn that the distortion uniquely identifies the lens used...

Nah, not likely. Unless you knew exactly what the scene was supposed to look like, from that exact angle and everything (and even then it would likely be impossible), you just can't know what is a distortion from the lens and what is part of the scene. Unless, like, the scene happened to be a highly accurate checkerboard pattern. Then you can look and see what lines aren't quite straight and get some distortion information, but that would be tough.

I know software can correct for lens distortion if it has a distortion profile for a certain lens (which is probably made by shooting a checkerboard type pattern...), but knowing to move every pixel to the left one is a lot easier than knowing if every pixel was moved to the left one by the lens, if that makes any sense.

Put another way, it's easy to put soda in your mouth and have yellow stuff come out of your underbits, but very difficult to do the reverse.
-Taylor

Re:Raw images?

[Speare]

You really don't need anything so clean and nice as a full-scene checkerboard, to calculate a lot of lens details. Two or three moderate-length manmade straight lines that are at different angles should be enough. Like two edges of a table, a tall building, etc. That should be enough to give you the general curvature coefficients, which in turn would be pretty close to giving the right field of view. I don't think you'd be able to tell Sigma from Canon from Nikkor from Leica from Tokina from Zeiss glass.