Re: [Gimp-user] how to darken bright areas

[Gene Heskett <gheskett shentel net>]

On Wednesday 04 January 2017 18:58:20 paulhurm wrote:

> > On Wednesday 04 January 2017 14:57:07 paulhurm wrote:
> > I don't know as I would call it silver creep. What it is chemically,
> > it
> > that the developer blacked silver, because of inadequate washing, has
> > reverted to the silver.
> >
> > I haven't personally seen enough of this to consider the obvious
> > solution, which would be to develop it again, with a modern
> > developer, Dektol if you can find it, perhaps even D-23 which ypu
> > have to make yourself, then a weak acetic acid stop bath for perhaps
> > a minute to neutralize the calcium carbonate accelerator in the
> > developer, then refix to get rid of any residual silver, 3 or 5
> > minutes, then wash in running tap water for half an hour or more to
> > remove the fixer, all at temps of 68 degrees or so. 75 works faster
> > if you can muster up the warm
> > water fast enough.  Then let air dry for at least an hour. I would
> > not use a heated dryer for that because it will take on the gloss
> > from its hard chromed surface. That will interfere with the
> > scanning.
> >
> > Yeah, I'm an old fart of 82 now, but I helped in the darkroom at my
> > local
> > weekly fishwrap since about 1947, and had my owm chemical darkroom,
> > B&W
> > and Color printing, for nearly 35 years starting in the late '60's.
> > So I
> > know a wee bit about this.  And while I have never done this, I'd
> > sure take one you could waste and see if this proceedure would help
> > mitigate
> > the effects of the aging. Locating the chemistry supply in 2017 will
> > take a determined search.
> > Cheers, Gene Heskett
>
> This discussion would probably be helpful in different circumstances
> but won't help with the ones I am faced with.
>
> I really want help with the scans so I did not give other details that
> should show that any further processing of these prints in not
> possible.
>
> I am actually working with photographs that are mounted into an album,
> not separate prints. This album is the "old style" with black paper
> pages onto which the photos were glued. Doing anything to re-wet would
> most likely destroy this album which should obviously be out of the
> question.
The black paper, and the glue, totally preclude any thoughts of its being 
an archival quality mounting medium.  There is some acid in all that 
stuff that old.

So you must do what can be done with the scans you have.

> Another aspect that I did not mention in my original post is that each
> of these pages has hand written captions next to each photo. Again,
> any wetting would probably destroy these which is also not acceptable.
>
> For others who may read this, again, I need help on how to work with
> the current scans I have. I am also not willing to do any re-scanning
> since some of the captions seem to be deteriorating and I don't want
> to handle the pages any more that is absolutely necessary.
>
> Thanks.
>
> Paul

You it appears, are truely between a rock, and a hard place.  The only 
other possible procedure would involved crafting a very narrow band 
color filter, centered on the silvery tint, which might be further 
filtered to recover its luminance detail, and re-add that detail to the 
K channel of a cmyk encoded copy of the original scan. I doubt that it 
could be scripted because of the variations in the aging of the 
individual print. Under the conditions you describe, you would probaby 
have to separate each print on the page into its own file for individual 
processing. You would need to develop a filenameing convention that 
included the page it was on, the upper left corner position marker, and 
the images own size, including any captions involved, so that once they 
were recovered as best as can be done, a relatively simple script could 
put it back together with everything in its original location for then 
making a single page image that could then be printed at high enough 
resolution that other researchers could learn from it. 

I don't envy that position...

How about you make an "unsharp mask", crank up the contrast, then print 
with the unsharp mask subtracted to reduce the contrast back to maybe 
20% more than you started with?  That might find usable detail you 
cannot see very well now.

Cheers, Gene Heskett
-- 
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