[filmscanners] RE: Color spaces for different purposes

["Laurie Solomon" <laurie@advancenet.net>]

>At this point it's moot
True, especially with regard to the original basis for the discussion. :-)
However, it may not be moot with respect to spin-off issues. :-)

> conversion from TIFF to JPG reduces file size and
>apparently compresses, I would think to Maximum quality.  Sharpening at
that
<point was what I was suggesting, before saving as a more-compressed JPG

Saving a file as a JPG file at a level of compression involving the least
amount of compression would obviously result in much less lost empirical
information (e.g., actual image data) than to save at higher compression
levels; however, I think it is questionable if the remaining empirical data
would represent maximum quality in all cases.  But to change the existing
data in the original JPG file by sharpening and then resaving the result to
a more compressed state is one of the sorts of actions which tends to
produce the often found JPG artifacts and deterioration of the image that
such a file can produce.  Obviously, the more often one changes the level of
compression in the resaving of an openned JPG file as well as the more
information that one changes between such compressions the greater the
possibility of artifacts and deterioration of the resulting image.  At
least, as far as the earlier versions of JPG ( cannot speak for JPG 2000),
the compression was a lossy operation in which algorithms were used during
compression to discard redundant data and to generate new data based on the
retained data and the algorithm upon expanding the file.  To recompress at a
new level means that one would be applying the algorithm to increased levels
of artificially created simulated data with each such resaving at a
different level.  Thus, the net result would be to be creating or
interpolating new data based on existing data that itself was artifically
created by a similar method with less and less of the data that makes up the
file being the original data from the capture.

-----Original Message-----
From: filmscanners_owner@halftone.co.uk
[mailto:filmscanners_owner@halftone.co.uk]On Behalf Of Maris V. Lidaka
Sr.
Sent: Saturday, June 08, 2002 4:40 PM
To: laurie@advancenet.net
Subject: [filmscanners] Re: Color spaces for different purposes


At this point it's moot since Ken said he resizes in TIFF and sharpens, but
I think you are correct - conversion from TIFF to JPG reduces file size and
apparently compresses, I would think to Maximum quality.  Sharpening at that
point was what I was suggesting, before saving as a more-compressed JPG.

Maris

----- Original Message -----
From: "Laurie Solomon" <laurie@advancenet.net>
To: <mlidaka@ameritech.net>
Sent: Saturday, June 08, 2002 3:35 PM
Subject: [filmscanners] RE: Color spaces for different purposes


Alas, either I am misunderstanding you or I am terribly confused; both
options are entirely possible.
>I would convert and sharpen before compressing
If you convert any file format to a JPG format, are you not coverting and
compressing at the same time?  I did not think that in fact they are
practically separate and distinct operations even if the act of coverting
presents itself to the user as if it were being done in stages.  Thus, if I
am correct about the conversion and compression processes being from the
users point of view for all intents and purposes one in the same, how does
one sharpen between the conversion stage and the compression stage?

> -----Original Message-----
> From: filmscanners_owner@halftone.co.uk
> [mailto:filmscanners_owner@halftone.co.uk]On Behalf Of Maris V. Lidaka
> Sr.
> Sent: Saturday, June 08, 2002 1:07 PM
> To: laurie@advancenet.net
> Subject: [filmscanners] Re: Color spaces for different purposes
>
>
> I would convert and sharpen before compressing.  It may or
> may not help -
> I'm not an expert - but it would deal with any artifacts that
> might possibly
> be introduced in the conversion process itself.  I would not compress,
> re-open and recompress absent drastic sharpening artifacts in
> the compressed
> JPG.
>
> Maris

[remainder snipped]


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