Digital BW, The Print

Evan,

You wrote:

>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?

It's totally subjective.  I get some curves such that all the patches of the
step wedge are right on their targets.  The next day a few will be 1% off.
When I'm adjusting curves I try to average the variance over multiple
iterations.  However, you really can't worry about 1% variances.  If there
is an obvious flat spot -- where two steps are really close visually -- then
that will have a negative impact on the image.  Tweaking the main curves
(usually the red curve -- cyan ink) is the best way to fix the problem.

>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?

I was tying to reserve the combined RGB curve for this.  One point in the
middle could do it easily.  I hear that more than minor changes could affect
the evenness of tones, etc., but give the RGB curve a try first.

Paul
http://www.PaulRoark.com