Archived posting to the Leica Users Group, 2006/08/27
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On Aug 27, 2006, at 11:35 AM, B. D. Colen wrote:
> Perhaps, Feli - I said I was sticking my neck out. But why the
> heavy jpg
> compression only in those areas where someone would be 'splicing
> things on'
> were it a fake?
Compression artifacts are most prominent where there is a large jump
in contrast.
Going from a constant black to an almost primary red of much greater
luminance
value is a big jump for the compression algorithm.
You don't create artifacts when you are cutting and pasting elements,
unless you are
pulling a key based on color or luminance and don't do a very good
job. And even then
any artifacts can be painted out by hand if you are only dealing with
a still frame.
Compression artifacts are a result of the algorithm deciding what
information to keep
and what to throw out and are introduced when you save the image.
;-)
Feli
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feli2@earthlink.net
www.elanphotos.com
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