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JPEG uses a lossy compression technology resulting in significant file-size
reduction in the compressed format. It generally re-assesses clusters of 8x8
pixels and adjusts colour values within these clusters.  The size of the
JPEG file does depend on the amount of compression applied to the file.
Especially for digital preservation purposes you'd need to be aware that
extreme compression (and reduction in file-size) can come at a significant
loss of image quality, as pixel values are recalculated/edited.

TIFFs even with LZW compression (which is lossless) will not match the file
size reduction achieved with JPEG compression.  

However, in a day and age where disk-space, storage is becoming cheaper
every day and storage size volumes are increasing, I'd put a question mark
against using JPEG for the purpose of using less storage space.  

Reviewing use of JPEG2000 which uses new compression algorithms afaik and
has a lossless compression option would be a better choice when image
quality must be maintained.  

For more info on JPEG2000 standard:
http://www.jpeg.org/jpeg2000/

For more info on TIFF:
http://partners.adobe.com/public/developer/tiff/index.html


----
Cari Jansen  BSc (Comm.&IT/Rec.Man)   
Adobe Certified Instructor - Print Specialist   
Member Adobe Solutions Network

Web:   www.carijansen.com



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For those of you who know much more about computers than I do - Are tiff
images or jpeg images bigger or are they about the same  size?
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