From: Jeffrey D. Mathias (jeffrey.d.mathias@worldnet.att.net)
Date: 06/10/00-09:24:14 PM Z
Nick Makris wrote:
> ... my question(s) deserve a specific answer.
> ...I have never prepared an Analog negative for use with PT/PD and therefore
> wonder how one would go about creating the equivalent of the digital
> negative with a PT/PD curve applied???...
The digital curve function can accomplish much more than any analog
technique as it allows for manipulation beyond what the materials can
reasonably perform. The most versatile analog functions come from the
use of masks which can selectively add densities to the shadows of a
positive or the highlights of a negative. Each piece of film can be
controlled with exposure, development (chemistry, concentration, time),
fogging, selective intensification or reduction of densities (and others
I've likely missed). A multitude of scenarios can be accomplished which
in effect, as the bottom line, alter the relationship curve of density
log exposure. This is what the digital curve function does.
Beyond the how is more importantly the why. No camera and piece of film
can produce exactly the densities need for a particular process to
replicate an original scene. There is always a compromise the
photographer must work within with any given materials. Further each
printing process will have its own set of sensitivity requirements which
to some extent must be meet if any control is to be achieved. For
example: a platinum coating has a different sensitivity then a g. silver
emulsion. In general this difference has been noted to almost always
demand a more contrasty negative for the platinum process to render a
"similar" result. (Similar is not identical because of unique qualities
inherent to each process.) Contrast adjustment is basically an
adjustment to the curve.
Any image will require some adjustment to the curve because of the
conditions during photographing, the lens and camera, the film used, the
processing used, the printing process and materials used, and the
personal preferences of the photographer. This adjustment can be
accomplished digitally with the curve function or by the analog
techniques mentioned above. Also layers can be used digitally, but this
is really the same as a curve adjustment.
> ...Also, how does this flat looking digital negative relate to the required
> "higher contrast requirement"???...
The inks of a digital negative may have different transmission
characteristics than film. Only the final print will demonstrate how
the negative really "looks". What you call flat is what your eye sees,
which is not what the print coating sees.
> ... the answer to this question will help clarify a
> nagging cloud (in my mind) over the basic philosphy one should be using to
> create a PT/PD negative (digital or analog).
The basic philosophy should be to understand thoroughly the materials
and processes used independent of whether the negative is digital or
analog.
-- Jeffrey D. Mathias http://home.att.net/~jeffrey.d.mathias/
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