From: Larry Roohr (lrryr@attbi.com)
Date: 07/03/02-07:22:17 AM Z
I'm not sure how pertinent this is to the current discussion but I'll throw
it in anyway.
I tried the spectral 'fill' method (orange neg) this weekend with a zia and
found that the resulting negative, when measured on my densitometer, gave
the same density results on each step of a step wedge as the 'all-color mix'
black negative did, I was surprised. Then when I printed it, as expected,
the orange provided a lot more density to the u.v. light, but the linear
gradation was shot. With the black negative I got even steps on the
densitometer/neg and even steps on the print, predictable and controlled.
Now I could create a curve to account for the paper response to the spectral
neg and straighten it out but it gets a lot more complicated, rather not go
there, I can only handle the 'testing' thing in short spurts.
The only reason for the spectral method is to get the density required for
PP printing anyway so, curiosity aside, I don't believe there's any reason
to go there for gum, just complicates the issue.
Larry
-----Original Message-----
From: Hamish Stewart [mailto:hamish@gumphoto.fsnet.co.uk]
Sent: Wednesday, July 03, 2002 2:10 AM
To: Alt Photo List
Subject: Re: Gum over Kallitype with Pyro negative
On 2/7/02 17:48, "Katharine Thayer" <kthayer@pacifier.com> wrote:
> I've posted a couple of test prints at the Bostick & Sullivan forum
> which show what I'm talking about with spectral density and gum. The
> test prints relate only to digital spectral density negatives, not to
> pyro negatives, but the issues are similar at least if not the same. I
> put it under Coffee House since everything posted to the Alt-Photo
> conference bounces back over here. It's there, for whatever it's worth
> to anyone; I get the feeling that maybe I'm the only one for whom this
> is an interesting question.
> Katharine Thayer
>
Katharine,
As someone who is about to embark on the digital neg process this subject is
of much interest. I have read Dan's book and would have planned to go the
spectral density route but for some of the comments on this list which
suggest that for gum at least plain black ink works best.
Your test prints in coffee house are very useful for me and illustrate well
the difference in response. For my eyes the black ink is definitely
superior.
This begs the question to all gum printers out there making digital negs.
Does anyone use the spectral density method successfully with gum?
As an aside I find that too much density for standard silver negs causes
problems for gum printing as well. Perhaps the problem with the spectral
density negs is related to density rather than colour ie if the spectral
density method is intended to increase the density of the negative for
printing processes with a longer curve than gum then perhaps this method is
also increasing the general density of the negative which may have something
to do with the contrast problems? I don't have an answer but your tests seem
conclusive Katherine. Thanks for sharing them!
Cheers
Hamish
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