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Archiver > TMG > 2008-07 > 1217346926


From: Ian Barker <>
Subject: Re: [TMG] OT saving digital images TIFF vs JPEG
Date: Tue, 29 Jul 2008 11:55:37 -0400


There is a very useful and simple summary of the pros and cons of the
various common image file types available at
http://www.scantips.com/basics09.html
Read page 1, then hit the links for TIF, PNG, JPG and GIF at the bottom
of the page.

Note that GIFs are better for displaying and printing line art, print
and black and white or colour graphics than JPGs, which are superior for
photographic images. Either TIFs or PNG files are recommended for
editing photo files and for archival quality photo images, since
manipulating and re-saving the image does not degrade quality, as
happens with "lossy" formats such as JPG. Though less used in general,
PNG images, which can be displayed on web pages, have quality comparable
to TIFs, which cannot be displayed on the web, and are more compressible.

Ian Barker


Date: Mon, 28 Jul 2008 23:07:51 -0400 (EDT)
From: Pierce Reid <>
Subject: Re: [TMG] OT saving digital images TIFF vs JPEG
To:
Message-ID: <>
Content-Type: text/plain; charset=iso-8859-1

JPEG files loose some of their "accuracy" when saved as a compressed
file. However, that is only important when you loose detail that you need.

When saving a document image, such as a census image, you basically want
to accurately read the text that is written on the document. The
precision that is normally provided by various image data base providers
is usually much more than you need to glean the information the creator
put on the paper.

I find that I can greatly reduce the file size without loosing any
useful detail. In fact, I have been able to reduce a file size of over 1
meg to more like 100 kbytes and I cannot detect any difference when
comparing the files magnified over 10 times.

If you have a program that lets you control the compression of JPEG
files, such as irfanview, you can experiment with different compressions
to see what causes a problem reading the information on the form.

Pierce


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