U of S | Mailing List Archive | alt-photo-process-l | Re: (Drumroll): gum prints w curved vs uncurved negs (Re: How many gum

Re: (Drumroll): gum prints w curved vs uncurved negs (Re: How many gumlayers (Re: ferri sesquichlorati)

If you have vuescan would scanning the image as a raw file help with this?

On 10/25/06, Michael Koch-Schulte <mkochsch@shaw.ca > wrote:
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.
----- 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.


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