Digital BW, The Print

Darrell:

--- In DigitalBlackandWhiteThePrint@y..., "darrelleifert" 
<darrelleifert@y...> wrote:

> I think I'm still a bit confused on several points (BTW, I am using 
> the MIS original inksets):

Aaah.  Just like your doctor, lawyer, and accountant, you need to 
divulge all the key facts to focus the advice you get (;>))

> > 1)  The apparent evenness of the false colors (CMY) applied to
> > your image is in no real way indicative of an even printed
> > grayscale.

> I understand that the CMY curves break up the print so that dark, 
> medium and light tones are printed by the appropriate cartridges.  
> But if a grayscale stepwedge does not print evenly, are changes
> best made to the CMY color curves (when the stepwedge is converted
> to color) or a single 19-step brightness curve when the image is in 
> grayscale mode?

First, its the RGB curves that partition the image and trick the 
Epson driver into thinking it is printing various shades of CYMK.

Second, I am a firm believer in going to the source.  I'd fix the 
partitioning curves, especially if there are significant "flat 
spots".  Some of the advantages of partitioning are lost if you tweak 
the image too much with a grayscale transfer curve (which is 
essentially what Woolf's and Nivin's lumped workflows do).  Other 
folks may have a different opinion.

 --snip
> > The positions of the inks in the MIS-Orig inkset are
> > Red/Cyan=light gray, Green/Magenta=dark gray, and
> > Blue/Yellow=medium gray.

> If the gray inks (25%, 50% and 75%) are keyed to CMY color values, 
> how can Red/Cyan, Green/Magenta and Blue/Yellow refer to the same 
> tone/tank?  Logically it seems that a "red" curve would use half 
> magenta and half yellow, meaning that a mix of the 75% and 50%
> tanks would print, not the exclusive 25% from a true Cyan curve.
> (I'm  really confused on this one.)

I am outside my area of expertise, but here is my understanding.  
Maybe someone in this forum can jump in and add or give us links to 
color theory/print driver primers.

Your monitor (and editing software) works in RGB additive light space 
(red light + green light = yellow light).  Your printer lays down 
dyes or pigments that absorb part of the incident light and reflect 
the rest (cyan ink absorbs all the red light and reflect the rest). 
The Epson driver converts the RGB image into CYMK space which 
controls the CYMK ink colors in the printer carts.  

I think it is now the time to invoke "faith based printing" and just 
say that adjusting the red curve in a .amp, .cvr, or .cc curve set 
controls the amount of cyan that shows up on your grayscale 
(converted to 24-bit) image displayed on your monitor when the curve 
is applied which in turns controls the ink in the printers cyan 
position no matter what color or shade of gray may be there, etc.  

Also for clarification, the MIS Origial Quadtone inkset labels are 
NOT related to the actual densities -- K = 100%, "75" = 96%, "50" = 
79%, "25" = 24%.  Your milage (densities) may vary--however these 
values are ball park.  Only MIS knows why the ink labels and actual 
densities are this way.

 --snip
> > 4)  I again recommend you gain experience modifying single curve 
> > workflows (i.e., lumped RGB workflow curves like Woolf's and 
> > Nivin's). I also recommend you turnoff the Epson driver color 
> > control.  Position doesn't seem to matter with these lumped 
> > workflows.

> <sigh>  I would like to work with a single curve workflow, but
> doing so with my older Epson 1520 produces very noticeble dots in
> the light areas of the print. On the other hand, applying Chris
> Brandon's 4t_eam.amp curve gave me very smooth, dotless light grays 
> but "clumped" darks and midtones.  I hope therefore that if I can 
> understand how he produced his original curves for the 1160, I can 
> modify them to work properly with my 1520.  
> 
> The profile_make2.pdf did clarify many of my original questions.

You really don't need to understand HOW Chris developed his curves.  
All you really need to do is look at his .amp curves (that you have 
converted to PW .cc--right?) and follow the outline presented in 
profiles_make2.pdf ( Files> Ink Sets, reviews and techniques> MIS 
FS ). For example, if you have a flat spot at 70-80% and the 
histogram shows the center of the spot is at 75%, then you would move 
the 70% control point up (lighter) and the 80% control point down 
(darker), reprint and scan your stepwedge to check to results. This 
is an easy process using Picture Windows and its superior 
curves/histogram feature.  It however, is labor, ink and paper 
intensive, but NOT rocket science.

You may want to reduce the number of control points in each of Chris' 
curves to 21.  This again is very easy using PW.  Convert 
the PhotoShop .amp file to a PW .cc file and use a text editor to 
whack out the "extra" control points.

Hope this helps keep you on the path that ultimately leads to the 
ability to create art.  

Jeff Randall