Digital BW, The Print

Hi all

Waiting for my first batch of UT ink for 1160 to arrive and was 
investigating new workflow. Here comes the stupid questions.

1) If you apply the tone curve as a layer what happens if you adjust 
the opacity of the layer? Does it fine tune the tone or completely 
cock it up? 

2) Would I be right in saying that to get the very best quality the 
curve should be applied to a 16 bit RGB image rather than 8 bit?

Many thanks in advance.

Peter Newbee