[X4U] Quality loss while copying

[Linda]

On 10/20/06 6:19 AM, Paul Moortgat wrote:

> A friend has a nasty problem.  He made web images in JPG from TIFF.
> He copied these several times from HD to HD in order to rearrange his
> harddisks.  When he opens these images, some of them are disturbed.
> They seems to have a lot of white dots. Like they're overexposed.
> He claims that this is done during the copying.  What can gone wrong?

.JPG is a lossy format. .TIFF is not. Every time you save a .JPG you lose
some of the data contained in it. .JPG ought to be used just as the very
final format -- not for a work in progress.

If that's not his problem, it's possible that files can be corrupted while
being copied, but I'd bet that he's losing data when he's saving his .JPGs.

<http://www.webopedia.com/DidYouKnow/Internet/2002/JPG_GIF_PNG.asp>

<http://www.scantips.com/basics9j.html>

Are his "white dots" around the perimeter of the graphic when he puts it on
a dark background as described on this page? (scroll down to the cartoon
about 2/3 of the way down the page): <http://www.r1ch.net/img-formats/>