What happens? - Removing Chromatic Aberration

[rabanito]

Example.
Image of a seagull plunging.
On the contour between the white head and the dark water there is a blue fringe.
Lateral Chromatic Aberration

I'm using Lightroom.
I go to the panel "Lens Correctios" and check "Remove Chromatic Aberration"
There is some improvement but not 100%
I check "Manual", take the Eyedropper and apply it to the remaining blue. A small adjustment on "Defringe" and the blue line goes away for good.

My question is "What did really happen?" Did LR just remove (or paint) the line at the edge or did it a "real" correction  to the image take place?
Just curious - Maybe somebody can redirect me to relevant literature?

[Slobodan Blagojevic]

It seems to me that particular color was just desaturated. But I don't really know.

[rabanito]

Thanks Slobodan.
Nobody seems to know...

[PeterAit]

Thanks Slobodan.
Nobody seems to know...

What would a "real" correction consist of? You cannot go back and redesign the lens!

[Martin Kristiansen]

Back in the mid 90’s before chromatic aberration correction existed as a tool we would identify the colour and then in the channels slightly expand or contract the individual channel we thought responsible. If for example we had a green fringe you could slightly reduce the green channel in size and visually see the fringe disappear.

It was long ago and I think you had to turn the image into something called a multi channel file before reassembling into a normal image file. I could be wrong on that but I have a vague recollection about it. Obviously it resulted in a small crop. It was a fairly blunt tool but with small MP count sensors and lenses designed purely with film in mind it served a purpose and seemed quite clever and almost miraculous.

Anyway when the reduce chromatic aberration thing came along I always assumed it was doing something along those lines. I never actually looked into it though. I was just super pleased to have the tool. 

[rabanito]

What would a "real" correction consist of? You cannot go back and redesign the lens!

Of course Peter.
I'm asking what does the SW do.
Something like asking what does, say, AI Sharpen to sharpen a soft picture, the idea behind it.
The fringes disappear. Does this affect the whole image or something? Something like that

I wouldn't have to redesign a lens, I just sell my Ferrari and buy a better one. And carry it 

[rabanito]

Back in the mid 90’s before chromatic aberration correction existed as a tool we would identify the colour and then in the channels slightly expand or contract the individual channel we thought responsible. If for example we had a green fringe you could slightly reduce the green channel in size and visually see the fringe disappear.

Thank you Martin. Very interesting.
I had really no idea and was wondering

[Rhossydd]

Does this affect the whole image or something?

It can do. I've seen it push out the complementary colour on the other side of fine detail with CA.
You can miss the effect as you're often studying the specific problem area and the consequential colour shifts happen in other areas.

[rabanito]

Thank you Rhossydd.
I tried it on a blue fringe and noticed some change on some yellow pixels on the other side.
Blue line on the edge head/dark water disppeared but something tiny happened to the yellow beak
But it was w a 800x  magnification.