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Old Jun 23, 2005, 10:19 AM   #1
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Hi all, I'm new here and recently migrated over to digital from film.

I've read quite a few of the articles in this forum and in particular this one below where the author said that JPEG images saved over and over again will result in losses each time.

Does the same apply when I copy, say, from my CF card to a portable storage device and then to a HDD ?


thanks for any advise!


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Old Jun 23, 2005, 10:43 AM   #2
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No, copying does not involve any further application of the jpeg compression algorithms so there is no loss. When a Jpeg image is opened, the JPEG routines 'uncompress' the file (but it cannot restore the data that was eliminated in the compression process) if the file is re-saved again as a Jpeg, it is RE-compressed (resulting in further data loss). Everytime the file is saved as a JPEG it is re-compressed and every time it is recompressed, what the compression routine considers to be redundant data is thrown away. Eventually, the file loses its structure and dissolves into noticible blocks and finally, into unrecognizable blobs.

That said, one or two saves isn't a problem...50 saves is a problem. So, if you are going to be doing major editing work with several 'saves' during the process...it is best to use a lossless format until you are finally ready to convert it back to JPEG.
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Old Jun 23, 2005, 11:57 AM   #3
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Meryl is 100% spot on !
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Old Jun 23, 2005, 12:35 PM   #4
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The quality you save at makes a big difference. You can do many highest quality saves and not see much deterioration. Lower quality saves accumulate artifacts faster.
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Old Jun 23, 2005, 8:50 PM   #5
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thanks for the educated reply guys! much appreciated
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