The perspective correction tool is what I was referring to in "sliders".
It is a clumsy method to correct distortion.
As is the "distortion slider".
Yes, they are fairly clumsy, I'm not disagreeing with that.
I'm aware that complex shapes are trivial,
Surely you mean "non-trivial"?
but the behaviour of light through a camera lens is not random.
It's not quite random (quantum physics temporarily ignored
), but if you pick an arbitrary camera lens, the behaviour of light appears
Even if e.g. Lightroom has a profile for a Nikon AF-S 50mm f/1.8G on a Nikon D3s, that does not mean that your
sample of the same lens is identical. Optically speaking the light will
take a different path through your lens, as compared to the profile.
The differences may be miniscule and invisible to even pixel peepers, or it may be easily identifiable.
Even so, correcting for distortions is not the same as correcting perspectives to match your artistic vision of what's "looking right". Only you
can make that decision.
I suppose what I'm saying is rather than try and play with a bunch of knobs to get the picture looking right, I'd rather tell LR what it should look like and have LR work out what it needs to do in order for the picture to look that way.
Unfortunately, at this stage of technological development, that means that you have to tell LR by using "a bunch of knobs", or have someone else do it for you.