Thilo is right to the extent that a density reading with a color densitometer, presumbably through the blue channel, will not give you a exact equivalent of the actual effective printing density range of the negative. That is because, as he rightly points out, the actual spectral sensitivty of VC papers and graded papers is different, and in fact even varies by manufacturer. And the matter is much more complicated for VC papers than for graded papers.

Experienced BTZS users who print in AZO know that readings of stained negatives with the blue channel will not give an exact effective printing. However, it will bring you very close and with some modification of develoment times based on actual field tests you can establish effective N, N+ and N- times for a variety of shooting situatioins a lot faster than with other testing methods.

As for alternative processes that depend primarily on UV light, the actual effective printing density of a stained negative is very, very close to the density range I get from a UV reading at 373 nanometers. This has proven true for me in carbon, kallitype and palladium printing.

Sandy King