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When you scanned the stepwedge did you adjust the
black points and white points? How might be the key. Kevin Bjorke recommends
doing this on a thread running on hybridphoto.com. Just where might take a
little guesswork. I'd try scanning with all automatic settings turned OFF in the
scanner software/driver and using CS2 to manually set them. Try trimming the
black point so it touches the 100 % square and the white point so it touches the
0 % and then run that through the second part of the program. That way you're
eliminating the extra head room at the dark and light end of the scanner's
range. The print looks flat as a pancake. The blacks are grey and there's no
detail in the middle.
~m
----- Original Message -----
Sent: Wednesday, October 25, 2006 2:43
PM
Subject: (Drumroll): gum prints w curved
vs uncurved negs (Re: How many gum layers (Re: ferri sesquichlorati)
Okay, I've posted a gum print made with a neg (from
ChartThrob)
geared to fit my emulsion and printing conditiions, next
to a print
made from the same file, no curve.
I printed
several templates and generated several curves from the
same
emulsion last night, because being a statistician, I needed to
convince myself that the curve for a particular emulsion would be
reliable and robust (in other words that minute variations in how I
mixed the emulsion or coated the paper or whatever would not skew
the
curve; this seemed to be the case, in other words the curve does
seem
to be robust to unessential differences. But I used up so
much
emulsion printing those templates that I had to mix up some
more
pigment mix this morning, and so I printed another
template and
generated another curve this morning for the new
mix. Even though it
was essentially the same mix, I wanted to
be sure that the curve I
was using was generated for the exact mix I
was using. Again, the
curve looked very much the same as the other
curves.
I made sure that I had the positives and negatives straight
(his
directions and labels are helpful in that regard) and the
"corrected"
file looked very much like his example of a "corrected"
file, so I
don't think I did something really stupidly wrong, but if
I did,
someone can tell me.
The curve is not a drastic curve,
and the two negatives differ from
each other not at all drastically,
but I could tell just by looking
at the corrected negative that it
would print flatter and darker than
the uncurved one, and so it
did.
Both prints and all the templates were exposed at 2 minutes, but
I
developed the "curved" print an hour longer than the other one
(if
I'd developed it the same amount of time as the other one, it
would
have looked even worse by comparison, but I wanted to give it
every
chance of turning into something, so I gave it some
leeway).
I spent something like 8 hours of my time and a bunch of paper
and
transparencies to end up with a worse print. I don't get
it.
http://www.pacifier.com/~kthayer/html/Curve.html
Katharine
On
Oct 25, 2006, at 10:28 AM, Ender100@aol.com wrote:
> Hi
Katherine,
>
> Whatever works for you is the way to
go.
>
> Mark
>
> In a message dated 10/25/06 10:50:56
AM, kthayer@pacifier.com
writes:
>
>
>>
>> > " Otherwise, why
not just start with an image, invert it and make
>> > a negative
of any unknown density without a curve and keep fiddling
>> > with
it until you get what you want in the print."
>> >
>>
> Best Wishes,
>> > Mark
Nelson
>>
>>
>> Well, indeed, why not.
Like Keith, this is exactly my approach and
>> as Keith says, it
works fine. And as Chris showed last week, it
>> works good for
her too. Her tricolor gum made from inverted uncurved
>>
channels was cyan-biased, but that's not a function of the curves,
>>
that's a function of the selectiion of pigment concentration of
the
>> three pigments in relation to each other. So I guess my
answer to
>> Mark's question "why not?" is, beats me!
Seems like a perfectly
>> reasonable approach to
me.
>>
>> But since Charles posted the link for ChartThrob
yesterday, I've been
>> playing around with generating curves some
myself, and like Keith, I
>> have to say, so far I like the "no
curve" approach better too.
>>
>> Recently, Mark, you said
that a beginner could save a lot of time,
>> money, and materials by
investing in a system for generating curves,
>> or better yet, two
systems. At the time, that didn't make sense to
>> me,
because the time and materials you "waste" in the beginning
>>
learning to print gum are "wasted" in the process of learning to
>>
print gum, not in the process of generating negatives, and you
still
>> have to learn how to print gum, no matter how you generate
your
>> negatives. So I'm not sure how it would make any
difference. And
>> besides, the way gum works, there's
very little waste; there's almost
>> no print that can't be salvaged;
pigment stain is the one exception,
>> and curves or no curves don't
have any bearing on pigment stain
>> But I didn't think there was any
point in arguing further, so I let
>> that thread die without saying
so.
>>
>> But now, after an evening of printing value
templates, I have to say
>> I think the savings are in the
other direction; you save more
>> materials by printing gum. At least
when you're actually printing
>> images, you have a print to work
with and do something with, and
>> chances are you can do something
with it, even if you didn't get it
>> "right" on the first
printing. But a template of value patches is
>> just a template
of value patches. And if I was really going to do
>> this, I'd
have to do it for every single different pigment I ever
>> use, at
every concentration I use it at, at every environmental
>> condition
(humidity, particularly)... I would be doing nothing but
>> printing
templates for the rest of my life, and there's not a thing
>> you can
do with the stupid things, except generate curves. Talk
>>
about waste of materials! I'd rather be printing
gum.
>>
>> I can't say yet whether the resulting curves
would be an improvement
>> over the uncurved negatives; I'm not even
there yet Will report in
>> due time with a
comparison.
>>
Katharine
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