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Author Topic: How to tell if a photograph is fake.  (Read 3868 times)

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namussi

« on: July 01, 2017, 21:51 »
0
http://www.bbc.com/future/story/20170629-the-hidden-signs-that-can-reveal-if-a-photo-is-fake

I found this passage particularly interesting.

Quote
Theres no such thing as a single jpeg format, explains Farid.

Law enforcement agencies often use this to help verify whether a picture has been altered since it was downloaded from the camera.

When you look into the packaging of a jpeg using code the order in which all the bits of information are ordered are very specific and are very different for Photoshop versus an iPhone versus Panasonic or Nikon, explains Farid. So we can look at the packaging of a file and say this has gone through Photoshop because there are these tell-tale signs.




http://www.bbc.com/future/story/20170629-the-hidden-signs-that-can-reveal-if-a-photo-is-fake


« Reply #1 on: July 01, 2017, 22:21 »
+1
I've always sort of assumed as much. Granted, the header information would mostly just make clear the file was saved in Photoshop, and that could mean you just resized it.

« Reply #2 on: July 02, 2017, 12:05 »
0
I've always sort of assumed as much. Granted, the header information would mostly just make clear the file was saved in Photoshop, and that could mean you just resized it.
You can strip out all that information I think.

« Reply #3 on: July 02, 2017, 19:33 »
+1
I've always sort of assumed as much. Granted, the header information would mostly just make clear the file was saved in Photoshop, and that could mean you just resized it.
You can strip out all that information I think.

The thing about it is though, even if you strip all meta and exif information, the bits still are all ordered the same for the same picture. It would be nice if photography software and stock sites alike would use that to "detect similar" information. Well, it would be identical actually, for a given length of bits.

They're getting better but, I'd imagine that software could eventually get to the point where it notices things like long strings of similar bits even for differently sized images.

« Reply #4 on: July 03, 2017, 00:35 »
0
You can (have to) open your raw in photoshop, ajust levels, reduce noise, etc... and export for the web in jpeg,
Is the photograph in this case considered as 'fake '?

« Reply #5 on: July 03, 2017, 02:21 »
+1
You can (have to) open your raw in photoshop, ajust levels, reduce noise, etc... and export for the web in jpeg,
Is the photograph in this case considered as 'fake '?
I don't think so seems to me the mere fact that it has been processed in photoshop, or whatever is not what people commonly mean when they say "photoshopped" i.e manipulated in some way to mislead.

« Reply #6 on: July 05, 2017, 08:38 »
0
IIRC, there is a standard for the way the data in a jpeg is written.


PS (I believe) writes the data in reverse, which is why (or perhaps it is so that) you can attach a clipping path to a PS jpeg.


Any of the other data EXIF. XMP, IPTC, etc. can be altered or removed.
I'm not a PS user, but I'm pretty sure that the "save for web" option strips most of it out.
 


 

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