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."

Re:Meta data?

[theNetImp]

I was going to say all my cameras have the make model and serial number built right into exif data of every photo I take.

Re:Meta data?

[afidel]

Yes, it's called EXIF and they are talking about a photo with the EXIF stripped.

Re:So What?

[fuzzyfuzzyfungus]

I hope the "there are 300 billion of them out there" defence works better for you than it did for certain owners of cheap, common watches [wikipedia.org].

Re:Oh my!

[winkydink]

No. Talking about my glass is showing off. :)

Re:Killjoy

[johnlcallaway]

My wife and I have two point and shoot cameras, a Nikon and an Olympus. We also have a Pentax dSLR.

Looking at the images at 100% scale and you can see a tremendous difference in the amount of noise in the backgrounds. That is mostly caused by the smaller size of the CCDs and the quality of the sensor itself. Plus, the higher end cameras have far better noise reduction software built in.

Depth of field is EVERYTHING to taking pictures. By using a long lens and a large aperture, bars around zoo cages disappear, the annoying crowd behind the bride also disappears, or that person just standing behind your subject gets just the faintest blur so your eye is drawn to the subject. Or use a small aperture and everything is brought into crisp focus.

Then there is being able to use higher quality optics. I recently used the Pentax camera to take some campfire scenes using a 50mm(film) lens set at 1.4f. I was able to take clear, handheld images around the campfire. Try that with a point and shoot.

I'm not knock the PS cameras. I use them when I'm riding my motorcycle to get action shots of those I ride with. That would be impossible with a dSLR or SLR camera, they are just too big and bulky.

But if someone wants to take high quality snapshots to share, nothing beats a dSLR. Pricey, yes. But well worth it for the serious photographer, be they professional or hobbyist.

Re:So What?

[mysidia]

Yes... CSI is very realistic in that regard.

Standard police tactic in real life, i'm sure.

Use fear/insinuation to get whatever info needed.

Except IRL it's not merely extortion, insinuated threats like that are all real.

Re:So What?

[Anonymous Coward]

The stuff you see on CSI and other similar crime shows is grossly unrealistic. It's actually so unrealistic that judges typically give a bit to jurors when they're in the panel that they should not put cops onto a standard compared against these shows (no one would ever get convicted). One of my judges used to put it something like this: "You need to understand the difference between reality and television. On these shows, the investigators find a footprint with blood, match it up to a boot tread, then find a butterfly wing elsewhere in the room, stick it into a computer, and 30 seconds later, they have conclusive proof beyond all doubt that the suspect did it. But in real life that will basically never happen. It is very likely that you may hear only testimonial evidence, and not see any photographs or any other physical evidence." And I cannot agree with him any more. I've NEVER even heard of an investigator going this deep to catch someone. Here's the problem -- your local police department probably has so many unsolved crimes, grossly insufficient funds, an extreme lack of sophistication, or a combination of the three. There's no way they can devote resources to do a forensic analysis to see what camera model took those digital pictures. In that same amount of time/resources, they can take 3 burglars and 10 crackheads off the streets. Meanwhile, if the government did try to present that evidence, the defense will bury the state in various motions (delaying the case), which is USUALLY a huge benefit to criminal defendants. Because the state usually has few resources to gather this CSI standard of evidence evidence, their cases are generally dependent on the testimony of victims/witnesses/cops, who often die/recant/move/retire/etc. Why would a state attorney want to risk losing testimony to gather forensic evidence that the jury won't understand and will probably be virtually irrelevant? I'm not saying that it's completely useless... but it'll probably happen MABYE once in the next 100 years.

- criminal defense attorney (not yours)

Re:Even after image manipulation?

[jools33]

There are photodesk editors with experience who claim to be able to identify the camera model, the lens used and the post processing software used to produce the jpeg / tif file. This is possible due to various characteristics that are introduced at each stage in the digital photographic process. Giveaways for the camera body used are the base resolution, any colour casts in the image, iso performance, dynamic range. For instance many Canon DSLRs are criticised for producing muddy greens in their images - especially at higher ISOs as the dynamic range is pushed to extremes. Then you can usually work out the lens - by the obvious field of view first, then the flaws in the shot - various lenses from various manufacturers have different flaws. For instance the 70-200 f/2.8 from Nikon has characteristic vignetting that can often be noticed even after post processing, then other cheaper lenses give various defects to the image such as chromatic aberation. The flaws in the image give away the body and lens. Also the sensor used gives certain image characteristics that are fairly easy to spot even to the keen amateur photogs eye - for instance telling the difference between a full frame sensor and a smaller APS sized sensor - the full frame image typically has a much smoother more film like attributes with less digital artifacts. Also the same can be said for post processing. This software usually leaves various characteristics - that remain with the image, and this varies for each different software vendor.

So this is all possible to a well trained human eye - don't see why it shouldn't be possible in software - but not sure of the real benefits of being able to identify this - as many photogs often leave the exif data - and that tells you everything.

Just discovered?

[Jason1729]

I read about this in Scientific American several months ago.

Re:So What?

[vux984]

As for laser printers, they can be identified uniquely because, on each page, they surreptitiously print a binary code (serial number, at least) in very small, light yellow dots. Yellow on white paper is nearly imperceptible. Wiki it for the whole story, including how to find and interpret the dots.

Yes, but even without that, you can match a printout to the drum, based solely on defects due to wear in the printer. The printer/paper equivalent of ballistics matching a bullet to the barrel it was fired through.

http://portal.acm.org/citation.cfm?id=1411332 [acm.org]

Re:stretch?

[HannethCom]

Because of how the Foveon X3 sensor works, if you have the full sized unprocessed picture, you might not be able to tell the brand of the camera used, but each individual camera probably has a distinctive blur pattern in the red and blue ranges, so if the forensics had the camera they'd be able to identify that specific camera was the one that took the picture.