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I am new to this forum.

Please look at the attached photo. It is a 40-year old photo of a river in Holland. I use Gimp regularly to restore old photos, but this one stumps me because:

1. The colors have faded
2. In addition to fading, there is discoloration (purple hue) in parts of the image that were probably exposed to sunlight.

This combination makes it particularly hard to restore.

The trick - I would guess - is to apply the color spectrum of the non-discolored areas to the discolored ones to generate a more uniformly colored photo. After that, one can do fine adjustments on the whole image.

Has anyone had experience fixing this kind of problem? What is the best approach?
What I did ( a quick try, not a perfect result but the photo is bad) :
- make a 2 copies from the original layer
- select the color blue on the copied 2 layer using : Colours / Desaturate / Mono mixer (use the sliders to convert the blue to black)
- the picture is a bad jpeg file, so blur the desaturated image (value 2 to 4)
- select the black color : Select / Select by color
- make the desaturated layer invisble to see the copied layer 1 below
- make corrections to the selection with different selection tools
- copy the selection to a new layer
- use Sample points on the selection and the rest of the picture ( the dark colour from the trees - see arrows)
- correct the values of the Sample points with the curves
- correct the selection layer with the levels
- make a new layer from visble
- use the healing tool to correct imperfections  
- Use Colours / Hue-Saturation to optimise or Colours / Rotate Colours
- Colorise if needed

[attachment=9575]
[attachment=9576]
What do you think about first converting to grayscale, and then colorizing it?

I've been playing around with this online colorizing app that offers a multitude of filters


https://palette.fm/


[Image: ZxAZ5GK.jpg]
For myself, I would be in favor of desaturating and re-coloring.  Recolor by hand if you have the artistic skills or use an online service if, like me, you have no such skills.

Unless someone is going to compare the damaged original side-by-side with the recolored version, they will tend to simply accept the recolored version -- despite all its flaws that make the retoucher cringe because it's nearly impossible to  "unsee" the flaws he knows were there.

I used the GMIC Black & White Desaturate Norm as it gave a smoother transition between the different original colors.  The GIMP desaturates didn't work as well.  

RikK: I'd never used palette.fm before, and the colorized version below was the "Base Palette", the first option of the 20 coloring options available.

From the original to the colorized version was a matter of minutes.

[attachment=9577]
[attachment=9588]
Very difficult image. It has been covered in two places where the colour seems to be impossible to get back.
Here is a sepia one
Thanks sallyanne, denzjos, rikk, neurolurker,

It seems that the consensus is to relinquish colors and to desaturate, and then either colourize or convert to sepia or similar. The picture is probably too bad to fuss over. Furthermore, the weather was really crappy the day the photo was taken, so there weren't many colors take pictures of.

I appreciate the effort everyone put into it (including denzjos with the detailed steps).

If there are new insights, I will update this thread.
(03-23-2023, 04:22 PM)rmiranda@inter.nl.net Wrote: [ -> ]Thanks sallyanne, denzjos, rikk, neurolurker,

It seems that the consensus is to relinquish colors and to desaturate, and then either colourize or convert to sepia or similar. The picture is probably too bad to fuss over. Furthermore, the weather was really crappy the day the photo was taken, so there weren't many colors take pictures of.

I appreciate the effort everyone put into it (including denzjos with the detailed steps).

If there are new insights, I will update this thread.
Greyscale is probably the way to go then. A Blak and white photo will do it justice