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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