Digital BW, The Print

--- In DigitalBlackandWhiteThePrint@yahoogroups.com, "esharamaki"
<esharamaki@...> wrote:
>
> I'm just trying to find some information regarding the difference 
> between a profile and curve when printing.  

this is actually somewhat complicated question. The answer tends to
depend on what printing software is being discussed.

When using QTR, one selects "curve" in the QTR interface itself.
Unfortunately sometimes these curves are referred to as profiles,
tending to confuse matters. With QTR comes QTR-Create-ICC, which
creates actual icc profiles. This is separate and different from the
various elements and included tools used for making ink descriptor
files and curves, and the resulting profiles used in the Photoshop
dialogue printing interface.
They are not interchangeable.

> 
> When using carbon-6, there are 6 different dilutions of ink.  Does the 
> profile control which "colors" or ink channels are used the way a curve 
> or a RIP controls which ink is used?

No, it does not (with caveats). But then again, some call the curves
profiles, making a definitive answer impossible.
The curves control how each individual ink is utilized, and also
usually includes and overall linearization correction. With QTR this
would be called a curve, Cone may call them profiles (even though they
are selected in the curve section of the driver), StudioPrint calls
this an environment, what other drivers and rips call it I don't know.

> 
> I guess I'm just curious in regards to printer function. I suppose that 
> the dilutions are not the same densities as their respective color 
> equivalents... If I were to randomly place ink positions, would a 
> profile take care of this?  

A real icc profile is simply used for mapping one color "space" to
another, based on known information of each. It has no way of knowing
we might prefer this lighter gray ink in the highlights than this
darker (so dottier) ink, best used for shadows. So those decisions are
made by you, and designed into the curve, or environment, etc. 
A monochromatic profile like QTR-Create-ICC makes, can still be used
for overall mapping from the file working space to the printer space,
which may or may not be necessary.

To add another layer of complexity, there are ways to edit your curves
into an icc profile, so basically all of the work is done there, and
sent to a NON monochromatic driver.... so the above caveat, and I
believe some of Paul's work may be done in this manner. Back when
there were only color drivers available, I played with it a lot as well.
Also, there are certainly normal icc profiling methods to characterize
 monochromatic device output, or optimize a color device's
monochromatic output.

BUT- a monochromatic driver like QTR, StudioPrint in mono mode, IJC,
and possibly others, generally utilize other ways to direct how each
ink is used for B&W, for example QTR curves, and StudioPrint environments.

These are muddy waters, hope I did not make it worse...
Tyler