Zorin's excellent post above exhibits far more technical knowledge about channels and layers etc, than I possess, and was the sort of help I hoping for when the thread was started .... for instance I didn't even know the issue
beutelwolf was asking about was called 'colour banding'.
My reference above to
'layers' was the fact that I know enough to be aware that the layers and similar adjustment techniques, are how all these issues are supposed to be corrected, but which I am largely ignorant of, as I have too little time to learn more ... And one look at the thread will show you that that's not too much more than cloning
... but I get by with that, a good eye for joins and a lot of patience.
Zorin got his '
quick and dirty and incomplete' results in 15 minutes .... my 'quick' results were well over an hour of fiddling about and trial and error
(hard work indeed!!) ... so its fairly obvious that his method of splitting the channels is the correct one, although there may be some more tweaks than that. ....
So I don't touch these types of pictures often, and few of those have turned out as I would want ... yesterdays was opportunely, an exception that proves the rule.
Extra Thought:
While I was in the pub last night I thought about this issue and Zorins post, and had a question.
Is it possible to replace the blue channel (in the example we are discussing), with one of the others ....renaming it 'blue' and changing it to blue?
I am probably exposing myself to some ridicule with this question, but I was thinking that by adding the corrected version (perhaps as a .. 'layer'
LOL), then that could perhaps correct the problem with no other intervention?
However one poster on a website thread on this banding issue said
"Sometimes, a little noise can help, but don't go above '6' generally. Other times you have to selectively blur and clone and heal and dodge and burn to remove it. Sometimes you have to do all of the above. If you can live without whatever you are doing to the file that is causing it, don't do it." .... which is pretty much back to my own 'hour of fiddling about and trial and error' .... ah well.