Re: Dynamic Range, was Re: Ziatype

["Jeffrey D. Mathias" <jeffrey.d.mathias@att.net>]

Sandy King wrote:
> What in the world do you mean by the "dynamic range" of a platinum
> variation? I have a pretty good understanding of the kind of
> negatives needed for different processes but really not a clue what
> you mean by this term.  Could you perhaps explain it in the common
> language of sensitometry that many of us could understand?

Dynamic range is the ["area", "distance", "space"] from maximum density
to minimum density.

Typically a negative will require a certain density when printing the
maximum black in the print so as to enable the proper printing of a Zone
I density in the print.  This is the minimum density in the negative for
the particular process scenario.

Typically a certain density is required to produce a pure white in the
print.  This is the negative's maximum density.

Now this does assume that one wishes a "full range" print with values
from pure black to pure white.

All the densities including and between the minimum negative density
(maximum print black) and the maximum negative density (pure white) are
the dynamic range of the negative (or print).

The "dynamic range" is a term I have borrowed from acoustics, but its
meaning is analogous to that used when dealing with sound.

Each Platinum process variation can require a differing dynamic range of
a negative to print a "normal" full range print.  In general, any
platinum variation will require a negative with greater dynamic range
than that used for the gelatin silver process or its variations.

Platinum variations can include pure Pt, pure Pd, mixtures of these,
various sensitizers, conditions, papers, chemical additives,
PrintOutProcess or DevelopOutProcess.

A greater dynamic range could mistakenly be thought of as a greater
contrast, but this is not true as contrast is really the slope of the
DlogE curve rather than the difference (or delta) between the end point
density values.

-- 
Jeffrey D. Mathias
http://home.att.net/~jeffrey.d.mathias/