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Explain the artifacts in this picture!

Asher Kelman

OPF Owner/Editor-in-Chief
The FBI released this picture from a video.

BostonSuspect18.4.13_.jpg


Explain the artifacts around the suspects and in front of the wall edge to the right but not the people in front. Have these figures been added in a composite to a new b.g. to obscure what the FBI knows. More pictures here

Asher
 

Jerome Marot

Well-known member
I would say that these artifacts look similar to the ones appearing in most video streams. You can't really compare stills extracted from a video stream to a well processed jpeg. Even if the principles behind the compressions are similar and the artifacts therefore also similar, video compression is optimized to be fast, not accurate and adds the intricacies of inter-frame compression. One gets more artifacts and typically on flat, detail-less zones as is the ground here. The processor keeps the bits for the zones with more details, which usually correspond to the subject, and the eye is not that sensitive to fugitive artifacts on flat zones.

It is of course possible that the pictures have been doctored, but it does not need to be so.
 
It looks to me that they have tried to increase the definition (for me, the contrast) of the particulars as opposite to the rest. Sure the image have been manipulated, but I can't see the trace of a new BG... Not that I am an expert through. It just resembles the result of CCTV footage I tried to enhance myself long time ago.

That the FBI cannot do better than me is reassuring in a sense :)
 
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