The biggest problem is that digital black and white is a single stage process, rather than a two stage one. When shooting B&W film you apply the colour filter at the point of exposure, to control the response of the film in the production of a "good" negative. Then once you have created the negative you would chose your printing paper, and of course the grade of paper would make a significant difference to the results too, just as your previous choice of film, filters, and exposure did. The of course you would have to expose the paper, plus any dodging or burning, or quite possibly dodging AND burning.
Producing a black and white image from a digital colour original is a completely different process, and although many of the terms are the same, the ones that I find potentially the least like the old way of doing things is simulating colour filters. Personally I much prefer to do my conversions in LR, since the mixer in LR gives you the most colour channels to work with. Even If I convert in PS I always use the Channel Mixer, not the Black and White filter. I also produced my own black and white presets in LR, which I have generally named for the colour filters that I might have used to get a similar result using film and a darkroom. Even when I have used one of my own presets, that is usually only a starting point, and I will make some fine
to at least some of the colour channels. The thing is that I usually just think about how the tones would have been rendered by FP4 or HP5, and then how that would relate to my print on either Kentmere or Ilford papers, and adjust the channel sliders to produce the result I would have got from film.
Alan
