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[OM] Re: file compression

Subject: [OM] Re: file compression
From: Gregg Iverson <golftooter@xxxxxxxxxxxx>
Date: Mon, 21 Jun 2004 12:26:18 -0400
My question concerned the sending of large jpg files over a phone 
connection.  I am also concerned that the receiving ISP might deny an email 
that contains a large attachment.  What does a zipped photo lose when it is 
opened?

Discussions of TIFF, JPG etc. have been covered.  I don't remember anything 
about  zipped files.

gregg

>An unanswerable question as posed. Some rough info:
>
>Compressed how? TIFF compression is limited, but lossless, so there
>would be no deterioration.
>
>Compressed how much? JPEG compression involves loss of information. But
>JPEG compression is adjustable from very high compression, with great
>loss of quality, to modest compression with essentially no visible
>quality change. At any given level of compression, the actual reduction
>in file size depends on the content of the image. The difference in file
>size from one end of the range of compression to the other is quite large.
>
>JPEG2 involves noticibly less image degradation at a given level of
>compression, but is far less common, probably because the developers
>want royalties.
>
>PNG is also a lossy compression tool that's supposed to be pretty good,
>at least for web images, but I don't know anything else about it.
>
>What do you mean by 'photo quality'? What medium, what size? What are
>your criteria for quality, and how do they compare to mine and others?
>It is quite clear from posting and comments on the list that images that
>are great technical/photo quality to some are junk to others.
>
>I don't have the answers to most of the myriad combinations, but  know
>enough to know it isn't an easy question with a simple answer. I think
>you pretty much have to experiment.
>
>Moose
>
>Gregg Iverson wrote:
>
> >Has anyone done a comparison of photo quality after compressing for
> >e-mailing vs. the uncompressed file?  I don't remember a discussion of this
> >topic, although I have been off the list a couple times over the past four
> >years
> >
>
>
>
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