Digital BW, The Print

Steve,

>...  When you ask your question do you simply
>show a big 50% step on screen and print (no other steps)?  ...

Of course, a single 50% patch would be rather meaningless.  But it's a place
to start.  The major "problem" is actually the way the monitors compress the
darkest few steps to the point that, in my view, it's just wasting our
limited grayscale.  If we had 16 bits through the entire process, that might
not be a serious issue, but with only 256 steps per channel in the final
step of the typical workflow, I think we need to utilize those that are near
the bottom of the range.  So, I use what I consider a more "linear" curve
than the monitors display unless other than the usual calibration is uses.


>> Most of the curves require that a grayscale file be converted to 
>>Adobe RGB first.  Then the RGB curves map to the CMY inks, 
>>black being generated by a combination of the curves.  
>>So, the RGB curves provide input-output relationships that 
>>allow me to specify the density of the image at each point.
>>It's just using Photoshop curves and the driver controls or built-in
>>characteristics (including cross-overs) to do most of what RIPs do.

>Yep.  I was wondering how mid grey (50% or 128) was modified.  
>I haven't seen any of your curves.

Download one of them and take a look.  See
http://home1.gte.net/res09aij/index.htm for my general index.  Of course,
you'll need to be familiar with the inkset densities for the curves to make
sense.

> How 50% maps to your print result is a function of
>(a) your curves and (b) the transfer function buried in the 
>Epson driver

All RIPs have a transfer function buried in them at some level.  I don't see
any one telling the  printer in machine code which dots to put where.  The
Epson driver is a RIP -- but with some "hard-wired" cross-overs (which are
excellent and useful if consistent with the desired results).

>even more complicated by the fact that the Epson driver is 
>expecting totally different inks.  So not transparent like a RIP ...

The Photoshop controls are more limited than a good RIP, but the differences
are a matter of degree.  There isn't that much difference.  The only place
I've been able to see a qualitative difference is where one needs to get
control of individual jets and avoid the built-in driver cross-overs.

The ink differences are largely taken care of in the inkset design, where I
work backwards from the printer and drive to the ink densities.  I prefer to
work with printers designed for pigments, because then the differences
between the OEM design assumptions and what I have available are minor.
It's amazing the dye printers work as well as they do.   But, again, since I
do the inkset design work also, I fit the 2 together.

The problems I have here are, for example, with what I'm doing now.  I'm
trying to work with an existing inkset -- the UT-FSN -- and make an inkset
that will print top notch matte and gloss prints on my 7500 and other large
format printers of that generation without the need to change the black ink.
The FS ink densities were never intended for this.  However, I've found that
only one new ink will be needed -- a medium gray that is denser than the
existing medium gray FS ink.  However, even here, where I'm not sure there
will be enough volume for MIS to be interested in making the inkset, I find
a way to easily mix the needed ink from exiting stock (in this case UT-FSN-M
and EZ-N).  But, so far, I'm finding the printer controls I have with the
Epson drive and Photoshop appear to give me what I need to do the job.

I'm not intending to restrict myself to the Epson driver.  When reasonably
priced RIPs can improve the situation, I'll use them.


> ...
>So the workflow becomes: 1. Get the image looking nice on screen ...
> save as file copy.  2. Apply a print curve which specifically takes 
>into account the tonal range of the ink/paper combo ...

That's it.

> ... 3.  Make any last minute, image specific adjustments - ...

I'd do this in #2. However, in reality, I always assume that I need to print
some draft prints and look at hard copy.  Not infrequently I make a slightly
modified curve for the specific print, saving it with the information I need
to identify it as a printing file for a specific paper, size, etc.  I just
don't think any monitor can take the place of viewing the print on paper. 


>...But it would be easier if we got what we were looking for when we
>push a button or shifted a curve.  That is, full logical transparency.

But that is where the skill and artistry comes in. 

Paul
www.PaulRoark.com