From: Jeffrey D. Mathias (jeffrey.d.mathias@worldnet.att.net)
Date: 02/01/01-11:26:59 AM Z
FotoDave@aol.com wrote:
> ...
> I personally think sandwiching digital negatives
> is not a good method. If two opague dots overlap
> each other, it doesn't add any density ...
> ... 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...
> ... True, each silver particle is opague, but the way it
> achieves density is different from digital negative....
My observation has been that no dots are visible in the print and the
effective densities do add. Resolution of 600 dpi, diffusion as you
state, and the texture of the paper perhaps all help. But the results
were fairly good except for the inability to address posterization.
Really, the prints showed the addition of digital densities to block
light similar to analog film. I will agree that an important key to the
sandwich with digital negatives is diffusion. (It's that fuzzy math
stuff.)
> << 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, ...
It is a different approach, but not necessarily better. Calibration is
much more complex and tedious. And the posterization is still a
problem. Consider also that the problem does not go away if arbitrary
new tones are created. The fact is that creation of tones as desired
relative to the original seeing is incredibly difficult and perhaps
impracticable.
> If you are interested in working together to get a curve/method for making
> Pt/Pd print with digital printer ...
The curves and method are not a problem. I have even outlined a nice
procedure for calibrating base curves. (Base curves being those
sensitometric, while artistic curves being personal choice.) Again, I
have made prints by both of the methods described. It is just that the
results are significantly inferior to what I have done with the analog
method. Inferior does not mean useless, but it does mean that
posterization remains a problem.
> ... 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).
That is a consideration I have not yet dealt with (making an analog
negative from a digital positive) and may have some merit. However,
consider that if the lighter inks are used in controlling the dark areas
of the print then that leaves the full capability of the darker inks to
address the upper values. Still much better than a single ink density
as posterization will be related to how many values (in the print) each
ink can produce.
-- Jeffrey D. Mathias http://home.att.net/~jeffrey.d.mathias/
This archive was generated by hypermail 2b30 : 03/06/01-04:55:37 PM Z CST