FotoDave@aol.com
Thu, 04 Mar 1999 21:52:50 -0500 (EST)
Hi Joao,
As I mentioned, I can't write long suggestions for now. I have been working
about 16 hours per day for the past 3 weeks, but I saw your message, so I will
try to give some brief answers first before I get to my suggestions later
(although once I start, sometimes there is no guarantee that it will be
short). :)
> I'll try increasing developer 1 first.
You can certainly try that, but it probably won't help much. The reason is, if
I remember correctly, the suggested first development is using paper developer
at normal strength for about 3 minutes, later recommended to be 5 mins. That
will give full or almost full development (by comparison, I have used Dektol
1+9 for 6 mins and that already gives full development because developing at 8
mins doesn't seem to change much contrast anymore except to raise the whole
density level a little bit).
> Yes, I want better contrast in highlights. I just imagined that if I could
> get the contrast i wanted in the first development, I could just overexpose
it
> to get to the final positive without the flashing step.
You could *if* the density range of your original negative is short. If you
develop the lith film with paper developer at full strength, you exposure
range is about 7-8 steps only! Say if you have a short-range negative. To make
positive, you could expose so that the whitest part is Dmin, but of course
that means highlights will fall into the toe region, so highlight separation
is not too good. The standard way is to expose it more so that highlights fall
into the linear region.
When you do reversal, you simply think everything in reverse (note I will
negate my sentence above): you could expose so that the blackest part is Dmax,
but of course that means shadows will fall into the shoulder region, so shadow
separation is not too good. The standard way is to expose it less so that
shadows fall into the linear region.
But that is assuming the density range of your original negatives is within
this 7-8 steps mentioned above. If this is true, then you can cover the whole
thing with exposure only without flashing (as you also suggested yourself). If
the density range of your negative is high, however, when you expose more to
get better highligh separation, you start to lose shadows, and vice versa.
Since I have talked with you about densitometry, I am assuming you are
familiar with film's curve, the typical S curve. People tend to think of
reversal processing as a completely different thing from normal development,
but it is actually the same thing, so for your analysis you can think of
reversal as normal processing but then invert it. Of course, for our "normal"
procsessing we get positives. That makes thinking even easier. (If you are not
extremely familiar with the characteristic curve and can visualize it in your
mind, it is best if you draw it out and put it in front of you as you think).
Now if the density range of your negative is longer than the exposure range of
lith film, you cannot cover the whole range, therefore you can use flashing to
help. However, flashing ***does not change overall contrast***. It only raises
the contrast of the low-density area (highlights of positive or shadows of
negatives) a little so that you can have better separation.... better compared
to the flat toe; but this is not the same thing as putting the highlights into
the linear region of the S curve. Are you following me so far? I wish I have a
pen and pencil in front of me and can talk to you directly right now. :)
But I know you are into densitometry, so this might be very clear. It is the
same principle of flashing that is used in zone system to give better *shadow*
separation but not changing the overall contrast. It is shadow in that case
because we are photographying positive images and get negatives. It is also
the same principle used in halftone photography where you use a flash exposure
to capture more range, but it does not change the overall contrast, just
capture a little more.
There are other possible solutions if you have long-range negatives, but
that's the part that I said I would get to later.
Ok, I got to stop.... I think it is better if it goes interactive. If there is
any unclear part, let me know.
Dave S
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