Digital BW, The Print

A few calibration questions from an MIS-VM user:

1. How close should a measured printout of a stepwedge come to the 
original values to be acceptable. Put another way, at what point 
should one use a transfer curve or other adjustment curve?

2. If a printed stepwedge is basically linear, but slightly (whatever 
that is) high or low, should one raise or lower the entire curve? 
What is the best method of doing this?

Thanks,

Evan Wolarsky