Digital BW, The Print

From: "Paul Roark" ...
>
>> If you want to start modifying the curves, print the 21-step test file to
>> see exactly where the problems are.  Then open the curve in question and
>> move the points where the problem is in the appropriate direction.  I
always
>> use the 0-256 (8-bit) scale, instead of the 0-100% ink scale, in order to
>> have better control.  The cyan curve is the one that gives the best
control
>> in the midtones.  Move the point about 3 units for each 1% that the
21-step
>> test print is off by.

Colin wrote,

>Which way should one move it?

When you are in the 0-255 mode curves (graph) dialogue box (mode switched by
the arrows in the horizontal axis), pure black is represented by (0,0),
which is at the bottom left of the graph.  White is the upper right corner
(255,255).

So, if you want to darken a patch on the 21-step test file print, go to that
point on, for example, the red (cyan ink) graph and move it down.  You have
to think in complimentary colors here.  The Red curve controls the cyan ink,
which is your main midtone ink.  Moving the point down makes the image
darker by adding more ink.

To get to the point on the graph that is of interest, you can use your
mouse, but be careful not to move the point when you click on it.  A safer
method is to use the control-tab key combination to move to the right, or
the control-shift-tab to move to the left along the graph.

> Also, the curves on my system are split into RGB not CMYK.

I found the CMYK controls do not give as good a control as the RGB controls.
Someone said that the Epson driver converts CMYK to RGB to send it to the
printer, and in that translation, you appear to lose good control of the
inks.

So, the black ink is controlled only indirectly by the combination of the
RGB curves.  The driver makes the decision to start bleeding in black ink,
and ultimately pulling out the "color" inks, by looking at where the RGB
inks are.  As all 3 RGB inks approach the black end of the graph, the system
starts to substitute black for color inks.  Because of this, smaller moves
of the points on the RGB inks starts to have more dramatic density effects
on the print as you approach the (0,0) pure black point.  In the darkest
quadrant, you'll get about 1% density change per 1 unit move of the Red
(cyan) ink point.

Hope this helps you fine tune your system.

Paul
http://www.PaulRoark.com

> starts to substitute black for color inks.  Because of this, smaller moves
> of the points on the RGB inks starts to have more dramatic density effects
> on the print as you approach the (0,0) pure black point.  In the darkest
> quadrant, you'll get about 1% density change per 1 unit move of the Red
> (cyan) ink point.
>
> Hope this helps you fine tune your system.
>
> Paul
> http://www.PaulRoark.com