Just work on the jpeg. As you say, this file is never modified so there is no quality loss depending on how many times you "edit" it, in the same session or multiple sessions.
Converting a jpeg to a lossless format before editing will give you zero advantages. When you export the file to a lossy format, like jpeg, there is a very small loss of quality. If you use a high quality setting during the export this loss will be so small to be practically none (especially if your original file was already compressed). If you really do not want this minimal loss export to png. The only case where you may want a lossless format is this: you open the file in DT, do some edits, export. Then open this exported file with gimp (or something else) and do some more edits. Now save with gimp and open the result with DT and do some more edits with DT. In this case there will be a very small difference if you use a lossless (png) format to "share" the edited file. In this scenario, in theory, using a huge 16 bit tiff file is even better but if your workflow starts with an 8-bit jpeg there is a minimal advantage in "adding bits" later (more or less depending on the specific image). Bye Lorenzo 2018-05-19 10:03 GMT+02:00 François Patte < [email protected]>: > Bonjour, > > If you open a jpeg photo in darktable, you can modify it (exposition, > contrast, etc.). As far as I understand the way dt works, the jpeg file > is not modified but all changes are recorded in the xmp file and a new > jpeg file is created when you export your photo at the end of the > treatment (am I right?). > > So my question is: is there some loss when I export the photo to a jpeg > file after treatment with dt and is there a cumulative loss of quality > if I reopen the original jpeg with dt (not the exported one) in order to > add or modify some module actions? > > What is the best strategy to work with dt on jpeg photos? Work directly > with the jpeg format or convert this one to another lossless format > (using imagemagick for instance) and work with this format before > exporting to the jpeg format? > > I expect that what I say is enough understandable.... > > Thank you. > > -- > François Patte > UFR de mathématiques et informatique > Laboratoire CNRS MAP5, UMR 8145 > Université Paris Descartes > 45, rue des Saints Pères > F-75270 Paris Cedex 06 > Tél. +33 (0)6 7892 5822 > http://www.math-info.univ-paris5.fr/~patte > > ____________________________________________________________________________ darktable user mailing list to unsubscribe send a mail to [email protected]
