The objective of this exercise is to create a black and white conversion then use the channels to lighten the complexion.
In the first image I have applied a default black and white selection layer over an image of Shellie:
The objective is to lighten the complexion without significantly altering the rest of the image. Since her skin is based on red and yellow tones I increased both those channels to create the second image:
This is better however this is a little simplistic so if we wanted to make a more lively image we can manipulate all of the controls including mid tones shadows and highlights along with structure and get something like this:
This has deeper blacks and more definition across the range, there are so many ways to manipulate an image from colour to black and white I am now of a mind that even when shooting film a colour film is more useful for the final conversion. This is a big shift in thinking for me and it has become a possibility only through the digital darkroom and it removes all the need for push processing and much of the elements of the zone system.