Digital BW, The Print

Paul,
>> What is a "physical density type negative?"
>

A physical density negative as I understand it is one that has 
density created by varying opacities of grey or grey/black ink.
 
> > The spectral density neg might be a possibility ..
> 

Spectral density refers to the apparent density as it relates to the 
sensitized media that is being printed on. Typically these are made 
with CMYK inksets. Since this technique mainly applies to printing 
processes that require UV light, different combinations of ink 
apllied to a transparency material will transmit or block actinic 
light. I suppose it could be used in silver gelatin printing also 
providing some type of masking for contrast control.

Don Bryant