Digital BW, The Print

Basically, in the end, all of the colour to B&W conversion
applications are more or less the same; they use variations in the
colour channels to shift tonality. The simple channel mixer style
approach suffers two pimary limitations, 1) it cannot maintain
luminosity while altering the intensity of a particular colour
filtering, and 2) it only works on primary colour filtration.

Personally, I prefer The Imaginingfactory "Convert to B&W Pro" but
thats merely a preference. However, like most of these applications it
DOES maintain luminosity while adjusting a single filtration colour
and it DOES offer both primary and secondary colour filtration options.

As for the additional control to emulate the tonality of particular
B&W emuslsions, this is really gimmicky as you are already beginning
with a modified tonal interpretation in the colour representation that
differs significantly from how the B&W emulsion would have responded.

The main point I wanted to make in this post is a technique for B&W
conversion from colour that I never see mentioned anywhere. Regardless
of whatever method or application you use, I often find that certain
parts of an image appear better under different filtration colours. As
an example, where a scene may basically work well with a yellow
filter, people with dark skin in the same image can appear much better
with some degree of red filtration.

The approach is to pre-filter the colour image (in Photoshop) for a
particular section and, if just one, mark it as a history state, or if
more, take snap shots. Then go to the state the satisfies the majority
of the image and by sequentially marking the other states as history,
paint these section back in with the history brush.

This is an example where multiple tone pre-filtering was necessary to
both stop the skin tones from being too dark and to provide tonal
separation between the coloured patterns on the dress:

http://flickr.com/photos/craygc/300148569/in/set-72157594381329667/

...but in conclusion, although I often like both the final result and
ease of starting with a colour image for B&W; I still think they lack
a level of luminosity or acctuance in the final image.

Craig