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From: Charles on 7 Feb 2010 17:13
Ran across some interesting posts about faked photos. Led me to this:

http://www.scientificamerican.com/article.cfm?id=5-ways-to-spot-a-fake

Then, ran across some opinions that RAW files cannot be faked? Wait a
minute! The demosaicing algorithms are public knowledge. Algorithms are
simply mathematical manipulations that surely are reversible. What am I
missing here?


From: C J Campbell on 7 Feb 2010 18:40
On 2010-02-07 14:13:31 -0800, "Charles" <charlesschuler(a)comcast.net> said:

> Ran across some interesting posts about faked photos. Led me to this:
>
> http://www.scientificamerican.com/article.cfm?id=5-ways-to-spot-a-fake
>
> Then, ran across some opinions that RAW files cannot be faked? Wait a
> minute! The demosaicing algorithms are public knowledge. Algorithms are
> simply mathematical manipulations that surely are reversible. What am I
> missing here?

Some Nikon DSLRs have a forensic marker that can be put in their NEF
files that makes it obvious if the file has been changed in any way.
People may be thinking of that. Nikon has a subsidiary called Nikon
Forensic Services which trains people in forensic photography and
performs other services.

Otherwise, what Alan said.

--
Waddling Eagle
World Famous Flight Instructor

From: Ray Fischer on 8 Feb 2010 01:08
C J Campbell <christophercampbellremovethis(a)hotmail.com> wrote:
> "Charles" <charlesschuler(a)comcast.net> said:

>> Ran across some interesting posts about faked photos. Led me to this:
>>
>> http://www.scientificamerican.com/article.cfm?id=5-ways-to-spot-a-fake
>>
>> Then, ran across some opinions that RAW files cannot be faked? Wait a
>> minute! The demosaicing algorithms are public knowledge. Algorithms are
>> simply mathematical manipulations that surely are reversible. What am I
>> missing here?
>
>Some Nikon DSLRs have a forensic marker that can be put in their NEF
>files that makes it obvious if the file has been changed in any way.

Ditto Canon. It's useful for police departments.

--
Ray Fischer
rfischer(a)sonic.net

From: Ofnuts on 8 Feb 2010 05:26
On 08/02/2010 07:08, Ray Fischer wrote:
> C J Campbell<christophercampbellremovethis(a)hotmail.com> wrote:
>> "Charles"<charlesschuler(a)comcast.net> said:
>
>>> Ran across some interesting posts about faked photos. Led me to this:
>>>
>>> http://www.scientificamerican.com/article.cfm?id=5-ways-to-spot-a-fake
>>>
>>> Then, ran across some opinions that RAW files cannot be faked? Wait a
>>> minute! The demosaicing algorithms are public knowledge. Algorithms are
>>> simply mathematical manipulations that surely are reversible. What am I
>>> missing here?
>>
>> Some Nikon DSLRs have a forensic marker that can be put in their NEF
>> files that makes it obvious if the file has been changed in any way.
>
> Ditto Canon. It's useful for police departments.
>

How does one detect that one is taking a picture of a printout of a
doctored picture?

--
Bertrand
From: Scott W on 8 Feb 2010 07:14
On Feb 8, 12:26 am, Ofnuts <o.f.n.u....(a)la.poste.net> wrote:
> On 08/02/2010 07:08, Ray Fischer wrote:
>
>
>
>
>
> > C J Campbell<christophercampbellremovet...(a)hotmail.com>  wrote:
> >> "Charles"<charlesschu...(a)comcast.net>  said:
>
> >>> Ran across some interesting posts about faked photos.  Led me to this:
>
> >>>http://www.scientificamerican.com/article.cfm?id=5-ways-to-spot-a-fake
>
> >>> Then, ran across some opinions that RAW files cannot be faked?  Wait a
> >>> minute!  The demosaicing algorithms are public knowledge.  Algorithms are
> >>> simply mathematical manipulations that surely are reversible.  What am I
> >>> missing here?
>
> >> Some Nikon DSLRs have a forensic marker that can be put in their NEF
> >> files that makes it obvious if the file has been changed in any way.
>
> > Ditto Canon.  It's useful for police departments.
>
> How does one detect that one is taking a picture of a printout of a
> doctored picture?
Very low dynamic range, a photo of a print is never going to look that
same as a original photo.

Scott

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