Digital BW, The Print

"Paul Roark" <paul.roark@v...> wrote:

>If you look at the red curve of the PS_FS1160a
> curve, you see a reduction of slope of the curve at about 55% (115 
input on the 256 scale).  

That where I think the black kicks in and was the basis (although 
weak) of my statement that all three inks should be greater than 50% 
(black = 100%).  The problem Alessandro was having was in the 80%+ 
area and thus probably not affected by the black kicking in, but 
curve generation is of course a lot of art with some science...

>What I
> have done on some curves is pull the lightest ink back from being 
on 100%.
> It is light enough that even a reverse slope can easily be overcome 
by the
> cyan ink.  If the lightest ink curve is raised enough, then the 
cyan ink can
> be more fully on and the lightest ink curve can be a "switch" for 
the black
> ink.  

Your pzoRGB4 curve that you shared with me did this.  I played with 
it for many milliliters of ink, but could not get it to smoothly 
transition or to to give me deep dark shadows so I went to the full 
on for the yellow and magenta position inks and let the cyan position 
ink curve control the dark gray and indirectly the black.


>That is, we are limited
> to 15 points per curve.  If there is a  bump between, for example, 
the "85%"
> and "80%" points, keep the points of one curves on those points, 
but move
> the points of another curve to midpoints, for example, the "82%" 
position.

Picture Windows users are not limited to 15 control points.  Also 
versions of PhotoShop that can generate AMP curves (as opposed to ARC 
curves in PS6.0) are not limited to 15 points (see Chris Brandin's 
curves).


> The more radical the curve
> slope is, the more these production differences seem to surface.

Agree 100%.  

Thanks.

Jeff Randall