Thanks Mike.
It is interesting to see which cameras support this feature (Distortion Control/Correction). Support for the old D90 is still on offer, whereas its more higly fancied siblings, such as the D3, D3S, D300, D300S and the D700 have never supported the feature.
I may be wrong here, but the chronology here is that the D3/D300 and D700 were introduced before the D90(which used the same sensor as the D300) .. so it's obviously something Nikon added to in camera processing once the D90 came to market.
It's the same with Nikon's Picture Controls(PC) .. I can't remember exactly which camera introduced the added 'Clarity' slider, but in the D800 twins you don't have it whereas in the D810 you do.
The difference between the two types of PC's is that the older cameras(eg. D800's) use an .NCP file extension whereas the newer cameras(with the Clarity feature) use an .NP2 file extension.
You can't load the newer .NP2 PC onto the older .NCP type cameras via the Picture Control editor.
But in Nikon's software you can use the newer type of PC on the older cameras.
Same with Picture Controls(which IIRC) were introduced with the D3/D300 .. cameras prior to those never used Picture Controls but had separate adjustment features for certain styles.
Again tho, in Nikon's software you could load a PC style onto an older (eg. D200 or D70) raw file as an alternative and forgot the in camera image enhancements.
It's simple progress .. and not really based on specs or model hierarchy.
As for it's use in Nikon software: If you enable distortion control in camera, then Nikon's software will read that bit and apply it to the image(the feature can be turned on/off in camera(at least in the D800E that I have). If you turn DC off tho, Nikon's software will respect that and not apply it to the raw image.
One thing I cant' remember tho(but I think happens) is, the DC if set to on, only works on Nikon lenses with detailed info fed to the camera(and hence exif). And the lens needs to be on the DC features list. So if you use a modern non Nikon lens, the DC is not applied to an image even tho DC in camera may be turned on.
And some (even modern) Nikon lenses weren't included in the firmware version prior to this one as I remember, so even some modern Nikon lenses may not have DC applied too.
eg. I remember the (then new) 18-140VR lens wasn't included in one of the earlier DC versions(it is in this one tho).
Furthermore, once applied in some Nikon software, I think it can't be 'unapplied'. I know in VNX2 this is true and no options to enable/disable any distortion feature at all. So whatever DC is applied in camera will be applied in VNX2 raw images.
In CaptureNX2 there is a Distortion Control feature, but it's not linked to in camera Distortion Control at all. It's just a slider that allows an amount of adjustment to an image.
But in CaptureNX-D, there is a Distortion Control tool under the Lens Adjustment tab. This seems to work with or without the camera DC feature too tho.
On a image from my son's D70s + 18-135VR lens, it applies what it deems to be the correct amount of distortion adjustment given the lens parameters in the exif. There are no controls to set the amount of distortion amount .. just on/off.
So it seems the same info for the camera firmware must be embedded into CNX-D as well .. and hence can be retrospectively be applied to an image via the editor.
Also note that on the Nikon software download pages for CNX-D and VNX-i there is a 3Mb file for updating the DC profiles for the software.
This update file has the same 'version' number that corresponds to the camera firmware version number(both being v2.013).
They are different files tho(and as such use different file names) .. they obviously aren't interchangeable files but must contain the same lens profile data.
As for ACR (or other third party software) reading embedded camera data such as this, or vignetting data .. I have no idea.