FotoDave@aol.com
Date: 02/01/01-08:27:07 AM Z
Hi Jeff and All,
<< Over the past year I have worked on two methods of making a digital
negative.
One, making three negatives of low, mid, and high density ranges
(scanning each partial range separately) and sandwiching them together
to print as one single negative. >>
I personally think sandwiching digital negatives is not a good method. If two
opague dots overlap each other, it doesn't add any density (well it does but
not for the printing purposes). The overlapped dots will block the same
amount of light. If two opague dots miss each other completely, then it adds
too much density.
For illustration purpose, just think of a traditionally screened/halftone
negative with 50% each coverage. If you make two of them, each should have a
density of 0.30 + b + f (because it is 50%). If you sandwich two of them, the
final density can go from 0.3 (if every dot happens to overlap the other on
the other negative) to 4.0 or more, that is, completely opague (if every dot
just happen to be one dot away from the one on the other negative).
Of course, if we use stochastic screen and because there is diffusion because
of the thick of the sandwich and diffused light source, the situation might
not be as extreme as shown in the example above, but it still illustrate the
points.
However, if you have two continous-tone negatives, each with density of 0.3
and you sandwich them, you get 0.6. That's why a few years ago I emphasized
the difference between analog and digital negative, though it has been badly
received. True, each silver particle is opague, but the way it achieves
density is different from digital negative. Each can be used, but we just
need to realize the difference.
<< And two, making three negatives to emphasize the low, mid, and high tone
portions (scanning full range with different gamma) and exposing them
one at a time onto a single coating. >>
I think this is a better approach, and I think it's probably just that you
haven't found the right combination yet. I believe that with the right
combinationm, you should be able to get full range without posterization that
you described, *but* even with smooth tone, I am not sure if you will be
completely satisfied with the result. I say this because I have seen quite a
few of your gorgeous Pt/Pd prints.
If you are interested in working together to get a curve/method for making
Pt/Pd print with digital printer, please email me offline. I don't do Pt/Pd
myself, but the principle is the same. And you have a lot of test
negatives/prints, both analog and digital, already, so we can start from
there.
>> Neither method was able to produce an acceptable Pt/Pd print. This also
gave me high expectations that an appropriate printer, driver, and
quad-inks might provide the solution I am after. >>
Well, we need to understand how the extra light-density ink is improving the
quality of the print. The additional ink might improve your *positive*
because it improves highlight, but it might not improve anything if you use
it to generate a negative because the beautiful improvement in the
*low-density* area now becomes the improvement in the shadow(!!!) which is
not the part that is giving problem.
Of course, if it is giving you satisfactory positive, then one possible way
is to generate the positive and then contact print in to a film (lith film
would be ok for this case because the density range is low in this case and
we would be using semi-halftone).
Dave S
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