* norman <[EMAIL PROTECTED]> [03-21-08 13:06]:
> I usually shoot in RAW and convert with UFraw plugged in GIMP. Then I
> have a choice of extensions to use for saving the file produced. I
> presume that if I use .xcf there is no compression and if I use .jpg
> there will be some compression. When working on the file I assume it is
> best to save as .xcf and not to use .jpg until the picture is finalised.
> I would like to know how the contents of the .jpg file so formed compare
> with the contents of a .jpg saved directly on the camera.
> The reason I ask is because I would like to use PTLens to remove CA but
> it seems that the software will only work with .jpg.

 *compression* is not the problem as such.  "lossey" compression is
the problem, you *lose* some of the definition of your object/picture
when you *save* it as jpg.  jpg is a lossey compression scheme.

If ptlens is your *only* choice, you have no choice except to perform
that operation as the last operation.  You will still have a minimum
of two lossey saves.

Patrick Shanahan         Plainfield, Indiana, USA        HOG # US1244711
http://wahoo.no-ip.org     Photo Album:  http://wahoo.no-ip.org/gallery2
Registered Linux User #207535                    @ http://counter.li.org
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