From: Sandy King (sanking@hubcap.clemson.edu)
Date: 03/26/01-08:27:58 PM Z
Judy Seigel wrote:
>Tom, don't forget Liam's reversal method -- I think that may have the
>least "limitation" -- and is streamlined in final "one flash fits all"
>version. It does require potassium dichromate and sulfuric acid, tho
>neither of those is obscure. Especially if you're doing a lot, so you
>get in the swing of it, maybe the least "removed" from the original?
>
Liam's reversal method as described in two different issue of Post Factory
works very well and gives cleaner negatives (at least for me) in that
dustspots are much less of a problem than with the negativ/postive/negative
procedure.
Unfortunately there is a problem with reversal processing that has not
previously received much attention. The problem is not in Liam's system,
but in reveral processing per se. Consider the following.
1. Virtually all lenses deliver less light at the corners of the image than
in the center. This is true to some extent with all lenses but the
differences can be especially great with wide-angle lenses, less with long
focus lenses.
2.Use of movements on cameras that allow adjustments such as shift, swing
and tilt can further increase the differences in illumination at different
corners or sides of the film plane.
3. When we make a print the lack of even illumination that was caused by
the taking lens is compensated for to a considerable extent by the
enlarging lens, which also delivers less light at the corners and edges
than in the center. In the course of making a print we typically correct
by dodging and burning in other parts of the image to correct for uneveness
of illumination.
4. The final densities of a reversal print are based on the initial
exposure (and of reverse order), in which the uneveness of illumination of
the camera lens and enlarger lens work together (rather than cancel each
other out as in printmaking). The result is that unless some doding or
burning is done in making the initial exposure the reversal negative will
in most instances increase the difference in illumination between the
center and the corners.
What I have observed in printing reversal negatives made by me and by
others is that they require considerably more work (dodging, burning) to
print correctly than in-camera negatives.
Sandy King
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