[filmscanners] RE: Archiving and when to sharpen (was:Color spaces for differentpurposes)

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

>Is it not lzw compression instead of lwz?

Yes, my fingers went faster than my mind when I wrote it. :-(

>Your comment that lzw compressed TIFF files are as small as JPGs made me
>wonder if you are working with graphic files and if they offer better
>compression than photos.

I must be candid and note that I was only repeating what others have said in
other discussions of file compression techniques and their comparative
advantages and limitations.  I personally tend to use Genuine Fractals with
photographic images and not JPEG or LZW.  My experiences in doing some of my
own testing suggests that (a) it depends on the image as to how comparable
the size of the file will be upon compression using LZW vr JPEG at level
10-12, (b) the level of quality (i.e., degree of artifacting and degradation
of the image) often is dependent on the degree of compression one uses when
saving as JPEG such that the compression needed to produce sizable
reductions in file sizes tends to result in a trade-off with respect to an
increase in image degradation, and (c) certain image enhancements do prior
to compression tends to effect the efficiency of the compression performed
by the different compression operations.

-----Original Message-----
From: filmscanners_owner@halftone.co.uk
[mailto:filmscanners_owner@halftone.co.uk]On Behalf Of Johnny Johnson
Sent: Sunday, June 09, 2002 2:10 PM
To: laurie@advancenet.net
Subject: [filmscanners] Re: Archiving and when to sharpen (was:Color
spaces for differentpurposes)


At 01:20 PM 6/9/02 -0500, Laurie Solomon wrote:

>Although I concur with all you have said, I have to wonder if the publicist
>and publisher are requesting jpeg files rather than lwz compressed TIFF
>files out of force of habit, lack of knowledgabout the ability to compress
>TIFFs using the lwz compression which is as good if not better than the JPG
>compression  at levels 10-12, or a lack of any real concern over quality of
>the file they are getting.

Hi Laurie,

Is it not lzw compression instead of lwz?  In any case, does the amount of
reduction in the file size using lzw compression vary considerably with the
content?  The reason I ask is that I just compared a scanned photograph of
3591 X 5472 pixel size saved in several formats.  The results were:

TIFF                            36,498 kb
TIFF with lwz compression       36, 523 kb
JPG @ Photoshop level 12        17,633 kb

Your comment that lzw compressed TIFF files are as small as JPGs made me
wonder if you are working with graphic files and if they offer better
compression than photos.

Later,
Johnny


__________________________
Johnny Johnson
Lilburn, GA
mailto:jjohnso4@attbi.com

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