Originally posted by Xcathdra
My other question is who did the analysis to confirm it was real?
These two experts are:
- Dr. Hany Farid, Professor of Computer Science at Dartmouth College and co-founder and CTO of Fourandsix Technologies & Kevin Connor, CEO of
You can read a very good estimation of the situation on his site here:
- Eduard de Kam, digital photography expert NIDF (Nederlands Instituut voor Digitale Fotografie)
As the discuss seems to take place here now , I'll quote my thoughts from the other
What I really would like to see is the full and technical analysis of Neal Krawetz.
Looking at its past work (especially in 2007
about the Al Qaeda propaganda) is
interesting as he seems to use the same tool (Error Level Analysis) to detect changes in JPEG compression (based on the quantization tables).
In the paper quoted above, Krawetz contradict himself several times saying that "two different logos with the same error levels indicate that they
were added at the same time
" after saying early that they were added one after the other, which is a utter non-sense, as it's only shows that the
JPEG compression level was the same for both items when they were added, independently of the date/hour.
So we can logically wondering if Neal Krawetz really know what he's talking about here.
I rather prefer the following assessment, from the forensic experts Hany Farid and Eduard de Kam
1. XMP Analysis. The XMP analysis reflects an incomplete understanding of the Photoshop metadata and also paraphrases the contents in a misleading
way. The referenced block of metadata merely indicates that the file was adjusted in the Adobe Photoshop Camera Raw module on multiple occasions
before it was opened in Photoshop and then saved out as a JPEG. In fact, this metadata does not track whether multiple files were composited.
2. Error Level Analysis. The forensic analysis of the JPEG compression as performed by error level analysis (ELA) does not provide a quantitative or
reliable analysis of photo manipulation. This analysis frequently mis-identifies authentic photos as altered and fails to identify altered images, and
as such is not a reliable forensic tool.
3. Shadow Analysis. The shadow analysis is flawed in its logic and conclusions. It is true that linear constraints that connect points on an object
with their corresponding points on the shadow should intersect at a single point (assuming the presence of a single light source). The location of
this intersection point, however, cannot be used to reason about the elevation of the light in the scene. The intersection point is simply the
projection of the light source into the image plane. This projected location can be anywhere in the image (including below the ground plane) depending
on where the photographer is oriented relative to the sun."
I totally agree with these three points.
ETA: Neal Krawetz stated that Hansen's photo is a composite, in the sense that it is made of parts from different versions of the same picture,
overlaid, and that the XMP blocks shows these manipulations by the Document Ancestors XMP tags that appears 4 times.
What Krawetz forgot to say (or maybe he don't know) is that there's no need to create a "composite" to obtain these XMP tags.
One of the key pieces of evidence cited in the initial article criticizing the photo is a block of Photoshop metadata which was said to indicate
that multiple files had been opened in Photoshop and combined. This claim immediately raised my suspicions, because I know from my 15 years working on
the Photoshop team that tracking metadata from multiple, composited photos is a challenge that the team has never really tackled. Typically, when one
photo is pasted into another, all of the metadata from the pasted photo is discarded.
As expected, when I examined the metadata in question, I discovered that it indicated nothing more damning than a file that had been
adjusted several times in the Adobe Photoshop Camera Raw dialog prior to being opened in the main Photoshop application and
saved out as a JPEG. To verify this, I succeeded in creating the same pattern of metadata in one of my own files by doing just that.
"Adjusted" is not exactly the same as "composited"...
edit on 16-5-2013 by elevenaugust because: (no reason given)