There are alterations of brightness in the blue sky, probably at the overlapping borders of the photographs.
These example pictures are stitched together from about 25 exposures. Nikon D70, 55 mm Micro-Nikkor at F 16 or 22. Exposure M Overlapping between the shots is approximately 1/3. The time for exposing the pano was approx. 1 min.
Rendering is with smartblend with default setting (Minimal Pyramidal 4, Transition smooth 0)
F 16 or 22. Exposure M. The time for exposing the pano was approx. 1 min.
If exposure values were identical for every shot in the series then using "NONE" as color mode is OK.
If exposure variations occurred and EXIF are available then be sure to use "LDR" color mode and have a look at the yellow anchor placement APP selects (if, for some reason, EXIF data are not available you should adjust brightness until the different shots are matched.)
Multiband is not as good as Smartblend is to hide vignetting but at F/16 or F/22 vignetting should not be visible.
the problem is solved. It was a selfmade problem: As I shot in manual mode, I set "none" as color correcion mode. Ithought it was a good idea, because I did not want to change the carefully adjused colors of the original shots. However slight brightnes variation became visible in this mode.
When I tried "LDR" the blue sky became smooth and the problem was solved.
As I worked in 16 bit mode, the finetuning of the colors of the final panorama was no problem.