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[filmscanners] RE: JPG sharpening [was: Color spaces for different purposes]



David,
I am not an engineer so I could very well be using terms that have
techincally precise meanings in imprecise commonsense everyday fashions.  By
"raw data," I only meant to designate the original data captured by the scan
prior to any compression; and thus, I was only trying to say that if one is
using lossy compression processes even at their minimum levle of compression
there must in principle be some loss of information so there theoretically
in principle must be more detail in the pre-compression data than in the
post compression data even if it is of no practical significance.  After
some posts by Anthony, it has become clear that he was talking in "for all
practical purposes" terms much like you are and with which I agree.

-----Original Message-----
From: filmscanners_owner@halftone.co.uk
[mailto:filmscanners_owner@halftone.co.uk]On Behalf Of David J.
Littleboy
Sent: Sunday, June 09, 2002 8:10 PM
To: laurie@advancenet.net
Subject: [filmscanners] Re: JPG sharpening [was: Color spaces for
different purposes]



"Laurie Solomon" <laurie@advancenet.net> asked:
>>>>>>>>>>>>>>
>Scans do not contain more detail than a low-compression JPEG can
>hold.

This statement I do not understand; please elaborate.  Surely, this cannot
be the case if we are talking about raw data as opposed to encoded
compressed data even at the lowest setting in which there still is some
compression of the raw data.
<<<<<<<<<<<<<<

The raw data is not truly random data. It is actually smoothly changing
nearly continuous data. So there is a lot of room for lossless compression.
Low-compression JPEG is very close to lossless compression, and only loses
information in areas of high detail and contrast. Since raw scan data
doesn't have such areas, JPEG works well.

David J. Littleboy
davidjl@gol.com
Tokyo, Japan




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