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<p>Hi Sveinn</p>
<p>Thank you for your detailed explanation and link to the technical
explanation. If I understand your solution seems to be in Gimp. I
will try and apply some of your methods and see where it takes me.
My main aim is to get decent usable photos right away with the
option of further tweaking the better ones after restoration. I
will report back here results. Meanwhile if there are any further
suggestions I would appreciate them.</p>
<p>TIA</p>
<p>Errol<br>
</p>
<div class="moz-cite-prefix">On 17/05/2021 14:57, Sveinn í Felli
wrote:<br>
</div>
<blockquote type="cite"
cite="mid:bad184cf-51d3-828c-2f2d-098c4529b387@fellsnet.is">Þann
12.5.2021 17:48, skrifaði Errol Sapir
<br>
<blockquote type="cite">Hi Gilles
<br>
<br>
The idea isn't to invert colour but to enhance colour. The
slides have faded and
<br>
the original colours aren't alive. The link shows a photo that
has faded.
<br>
<br>
Errol
<br>
<br>
<a class="moz-txt-link-freetext" href="https://mega.nz/file/QxlEAIbI#gwt5Omb5cSa1-WPeDxVlTdtyoNkwZYdeUC9xVp9L6b4">https://mega.nz/file/QxlEAIbI#gwt5Omb5cSa1-WPeDxVlTdtyoNkwZYdeUC9xVp9L6b4</a>
<br>
<br>
</blockquote>
<br>
Hi Errol,
<br>
<br>
Scanning and repairing old slides can be a complex matter; it
depends on brands of film, on previous storage of the slides, and
on type of mount (what kind of frame they've been mounted in), and
possibly other factors too.
<br>
<br>
I've repaired several slides similar to the one you shared, guess
this one is an AGFA-GEVAERT positive film, possibly a FUJIFILM.
Sometimes a generic automatic filter like "Equalize" will do the
trick; problem is that often a great deal of image info will be
lost. Other problem is that usually not all the original photos
were ever "correctly" exposed.
<br>
Existential problem; do you want to be faithful to the original
images or just get decent usable photos right away?
<br>
<br>
I searched the web thoroughly for info on how to do this with
FOSS-software; there are some scripts (mostly for GIMP) for
certain types of film of certain age (yes, the year of production
counts), but the majority of those doing such work resort to using
the commercial extensions available for Photoshop. Those are sort
of databases with measured decay of various types of film, along
with commands for corresponding filters.
<br>
<br>
Nevertheless I found a neat procedure for doing this in GIMP
(can't find the source right now); Take one of a batch similar
slides (from one shooting, one year or similar exposure), demount
it from the plastic frame (bad luck if it's glued into a paper
frame) and scan the whole area, including the perforated strip on
both sides, where normally there should be markings in clear
letters with the brand name and number of the image.
<br>
<br>
In "Levels" histogram mode with the eyedropper-tool in "All
channels" section, change the white-point to a decent sample of a
letter on the strip (transparent = white), similarly take the
black-point from the surrounding black/opaque frame, then pick a
gray-point (where a gray area should be) from the image itself.
This way you're compensating for the "natural" decay of the
corresponding film (of a certain brand, certain age). You may then
have to fiddle with all the color-components separately to further
enhance colors. The most important is to save the result as a
preset, and then use that preset manually on each image (with
further enhancements like sharpening etc.) or use it on several
images with GIMP --headless on the command line.
<br>
<br>
You could also use the values from this preset to make settings
for the BatchQueue Manager in Digikam or some script for
ImageMagick.
<br>
<br>
But as stated above, this procedure only compensates for the
natural decay of the film itself, not the decoloration of the
image due to sunlight or overuse (number of passages in a
projector).
<br>
<br>
For those who like the technical side of things:
<a class="moz-txt-link-rfc2396E" href="http://www.lionhouse.plus.com/photorestore/Restore2.pdf"><http://www.lionhouse.plus.com/photorestore/Restore2.pdf></a>
<br>
<br>
Good luck,
<br>
<br>
Just some thoughts - good luck restoring your slides,
<br>
Sveinn í Felli
<br>
<br>
<br>
<blockquote type="cite">On 12/05/2021 11:50, Gilles Caulier wrote:
<br>
<blockquote type="cite">
<br>
<br>
Le mer. 12 mai 2021 à 04:39, Errol Sapir <<a class="moz-txt-link-abbreviated" href="mailto:errol@tzora.co.il">errol@tzora.co.il</a>
<a class="moz-txt-link-rfc2396E" href="mailto:errol@tzora.co.il"><mailto:errol@tzora.co.il></a>> a écrit :
<br>
<br>
Hi All
<br>
<br>
I am now trying Manjaro KDE after many years of Kununtu.
Of course I am
<br>
also planning to transfer (or redo) my Digikam from
Kubuntu to Manjaro. I
<br>
have however a photo question that doesn't specifically
apply specifically
<br>
to either of these programs. As I said in the subject I
hope it isn't OT
<br>
but as it is photo connected and I hope Digikam can help
as well I would
<br>
appreciate the help of anyone who can. If it is OT the
moderators can
<br>
remove my post and I will understand.
<br>
<br>
I am transferring all my slides (and eventually negatives)
to digital
<br>
format. I am looking for a one-click solution (program)
that will restore
<br>
colours back to normal.
<br>
<br>
<br>
<br>
You want mean to invert color ? If yes, ImageMagick is your
friend, especially -negate option:
<br>
<br>
<a class="moz-txt-link-freetext" href="https://superuser.com/questions/1194468/invert-colors-with-imagemagick">https://superuser.com/questions/1194468/invert-colors-with-imagemagick</a>
<br>
<br>
This can be scripted of course to parse and process
automatically all files from your collection. And of course,
all can be done de facto under Linux from command line.
<br>
<br>
Else, In digiKam, Invert Color tool from Batch Queue Manager
can be used. Create a new Queue, assign items to process,
configure the output options (path, file name, etc...), assign
Invert tool + the convert format if necessary, and... you can
take a coffee.
<br>
<br>
Best
<br>
<br>
Gilles Caulier
<br>
<br>
</blockquote>
<br>
</blockquote>
<br>
</blockquote>
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