Digital BW, The Print

Thank you Lou.  

This is excellent!  I'll go have a look at Bruce's
website this evening.

My next "Back to Basics" question was going to be
about Lab, but maybe I'll find my answers there.

Thanks again,

Ken


--- Louis Dina <lou@...> wrote:

> Ken, comments are below your questions.  
> 
> Lou
> 
> --- In DigitalBlackandWhiteThePrint@yahoogroups.com,
> Ken Alexander
> <k.alexander@...> wrote:
> >
> > Hi Everyone,
> > 
> > I feel funny asking this after successfully
> printing
> > in black and white for so long, but I'm still
> trying
> > to get a firm grasp on what Dmax is.  My (probably
> > oversimplified) understanding is that it is the
> > maximum darkness (density?) that a given
> combination
> > of paper and ink can achieve.
> 
> That is correct.  Each printer/paper/ink combination
> has a maximum
> black it can achieve (often called Dmax).  The paper
> and ink are
> obvious contributors, but the printer can also have
> an impact. 
> Different dithering, resolution, number of passes,
> etc, can affect the
> ability to achieve a solid black.  Too much ink, or
> incorrect
> combinations of ink, can result in pooling,
> fogginess, and reduced Dmax.  
> 
> > 
> > What I still don't understand is:
> > - how is it measured?
> > - what units is Dmax expressed in, or is it a
> > dimensionless number?
> 
> Print Density is usually measured with a
> densitometer or a
> spectrophotometer.  It is often expressed in density
> units, but also
> in L* units(the L* component of Lab, ie, Lightness).
>  They are two
> different ways of expressing the exact same Dmax. 
> Since Lab space is
> often used as the universal translator for printer
> profiles, and most
> spectros read Lab data, it is often used, but both
> units are widely
> used.  
> 
> > 
> > I did try googling Dmax a while back but wasn't
> really
> > satisfied with what I found, especially regarding
> the
> > two questions above.
> 
> A great place to learn more (and see a translation
> graph that equates
> L* and density) visit http://www.BruceLindbloom.com.
>  Click the
> "Calculators" link, and then "Companding
> Calculators".  If you click
> density as the input and L* as the output (or vice
> versa) you will see
> a graph that converts from one to the other.  You
> can also input
> specific values to convert back and forth.  A
> density of 2.2, for
> example, is equivalent to L* = 5.6994.  The
> calculator also lets you
> see density expressed in Y units, or your choice of
> two different
> gammas.  Pretty flexible.  
> 
> Bruce also has a lot of articles, formulas and other
> information on
> his site related to color, density, color
> management, etc.  It gets a
> bit geeky fast, but it is loaded with tons of good
> information.
> 
> 
> 
> 
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