Expand the "Adjustments" section in the Lift & Stamp HUD and delete the line "Straighten" after lifting and before stamping.
(Lift & Stamp can be refined this way with all settings it handles.)
For spots in skies (and forests ), I find "Repair" works as well as, and easier than, "Clone". Leave checked "Automatically choose source". If the spot is circular-ish, I check "Detect edges" as well. I leave "Opacity" set to "1", and use as much softness as the Image allows, up to "0.5" which has proven to be more than enough.
Stamp the Images you want to fix, and then manually examine each to make sure the repair didn't make things worse.
From the images, and the fact that the spot went away, the only conclusion I can draw is grease or some other substance, perhaps not visible, on the lens. (Added: Fwiw, that kind of larger, softer, more generalized mark is not, IME, indicative of sensor dirt. If it were a removable-lens camera, I'd suggest cleaning the back of the lens as well -- but it's not. The only thing left is the front of the lens. Were you using a screw-on filter by any chance?)
(Added: Pretty color, btw. I think I saw in your "location" here in Apple Discussions that you were in Russia -- is that where these exposures were recorded?)
Message was edited by: Kirby Krieger
Thanks a lot, Kirby, for getting back to me so quickly.
and delete the line "Straighten" after lifting and before stamping.
and you made me actually read the manual again, to find out how to delete the line ...
I never noticed, that you can do more than just deselect adjustments, that you do not want to stamp.
I find "Repair" works as well
I'll try that, sounds promising, thanks for the hint.
Fwiw, that kind of larger, softer, more generalized mark is not, IME, indicative of sensor dirt.
I sincerely hope so - I am very attached to that camera.
The only thing left is the front of the lens. Were you using a screw-on filter by any chance?
No, on that camera I do not have a filter; but I'll give the lens a thorough cleaning. Perhaps there have been frost patterns temporarily, that I did not notice?
As you guessed, I have been in Russia for a conference, in a charming little town called Tarusa, south of Moscow. I have not had an opportunity to take pictures of ice and snow for a long time, and that is why I really want to save those shots.
Thank you so much for your help!