||Black/White/Neutral Control Points|
A neutral control point should only be used to correct minor mixed-lighting color
casts in your photo, after properly correcting for White Balance
under 'Develop'. Or, if you only have a JPEG (no NEF), this is you only choice for quickly
correcting color casts.
To visually see why correcting a color cast in a NEF is better done
via White Balance (which has access to all the bits in the NEF), instead
of a neutral control point (which only has access to a subset of the NEF info),
go into White Balance and intentionally introduce a major color cast.
Then attempt to correct via a neutral control point. The quality is
visibly not nearly as good as White Balance!
To use, click on the neutral control point icon, then click on a neutral point
inside your photo. After adding the control point, you can click and drag to
move the point to fine-tune the correction.
Black/White Control Points
A black control point is almost always used along with a white control
point. The purpose is to define the blackest point in your photo and
the whitest point in your photo -- so that the rest of your photo is
expanded to that dynamic range.
If NX101.com helps you, help this site by making a donation.
Also, because you are defining what 'should' be white and black, color
casts are also corrected.
This is often used with the double threshold in the histogram view to find
the blackest and whitest points in your photo.
Just click on the black (or white) control point icon, then click on the
point in your photo that should be the blackest (or whitest). After adding
the control point, you can click and drag to move the point.
Often times, a Levels & Curves can also used to adjust the dynamic range
of a photo (which also has black, white, and neutral color droppers).
Watch Video on using Black and White Control Points (by Nikon)