Rather than using the obvious Filter>Black and white conversion, I have been using Filter>photo effects, then 'tinted' in the drop down menu. This leaves you free to choose the tint exactly rather than a preset, but less obviously using the colour range sliders enables an optimisation of contrasts better than the spectrum type filter.

Lastly add a tip passed on by Duncan: alter the colour temperature in tandem. Although it is basically like altering the yellow-blue colour scale, it works at the RAW stage and sort of isn't quite the same.

Intuitive dabbling needed. method used in
http://www.worldphotographyforum.com...606&ppuser=780 &
http://www.worldphotographyforum.com...607&ppuser=780 & more in pbase gallery 'silver_sea'