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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...
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.
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Film can be identified down to the batch, MUCH more unique than a highly quality controlled part like a CMOS sensor.
There are 4 boxes to use in the defense of liberty: soap, ballot, jury, ammo. Use in that order. Starting now.
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.
> Of course someone who is stripping the exif data will never resize the image and run
> some sharpening over the image just to cover their traces, right?
Some will, some won't. Criminals are notoriously careless and stupid.
> Yep, this one was taken by a Canon Powershot A510 of which only 5.7 million were sold.
> We also know that this particular model was either sold in North America, Japan, Europe,
> Africa, Australia, South East Asia and South America. That should narrow it down.
Yes. Of the 18 initial suspects only two own that camera. Concentrate your investigation on them.
Warning: this article may contain humor, sarcasm, parody, and perhaps even irony. Read at your own risk.
That isn't the conclusion that the author came to. If you compare http://www.luminous-landscape.com/images-85/h2.jpg and http://www.luminous-landscape.com/images-85/g10-comp.jpg there is definitely a different between the yellows and the depth of focus on the expensive camera is far better (compare the red leaves on the upper left).
Depth of field isn't a question of better or worse, you know, it's just different. If you want to poke at that story, you might just point out that a the limited image size makes the comparison pointless. These days, cheap digital cameras make incredibly expensive pro cameras more useful for either flexibility or niche markets (like >13" prints). That doesn't mean professional cameras aren't worth it, just that they're not worth it for everything.
"I zero-index my hamsters" - Willtor (147206)
Cops didn't realize that most pictures posted on the interweb thing are usually post processed.
it is only after a long journey that you know the strength of the horse.
or you could just use a camera with a Foveon X3 sensor. there's no demosaicing involved since it employs 3 vertically stacked photodiodes (red, green, blue) at each pixel sensor to capture color information.
here is a diagram showing how a multijunction photosensor works. unlike bayer filter sensors, Foveon X3 sensors produce no color artifacts.
But then wouldn't the lack of demosaicing itself be the tell-tale sign that it was taken with a Foveon X3 sensor?
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.
In addition to noise, the small digitals show lots of other image degradation as compared to a dSLR. They lack sharpness and have issues with distortion, color accuracy and chromatic aberration. The ultimate source of all of those issues is the glass. You simply can't get the same level of quality out of a half-inch lens as out of series of two-inch lenses (assuming similar technology applied to both).
I just shake my head at the ever-increasing megapixel numbers on compact digital cameras. I know they're great for marketing, but for the camera owners they do nothing but produce bigger files, with no better image quality than if they'd had a smaller pixel count. Once you get beyond the resolution of the glass, there's just no point in adding more pixels.
I just read the Haselblad/Canon comparison, though, and I have to point out that the Canon G10 is not what most people think of when you say "cheap digital". It's not an SLR, but it's close, with larger, better glass than most P&S cameras and a larger sensor. 15MP is a bit much for those lenses and that sensor size, but it's not that crazy.
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At first blush this struck me as similar to the printers that revealed a specific device by a faint set of dots printed on each piece of paper. On further thought, it occurs to me that the difference would be that the dot-tracking was shady where-as this is a triumph of statistical observation. The former being slimy and the latter sheer brilliance.
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Add to that the fact that reducing the image size will probably get rid of the evidence, using a raw image and demosaicing on a PC will tell you what software was used instead of what camera was used, there are a lot of limitations.
On the other hand, most people do not know all this - then again, most people are unlikely to think of deleting the meta-data either.