Color correction on old Slide Scans

FloRolf · January 1, 2022

Hello people of LTT,

Today i have a somewhat unusual question.

I am trying to color correct slide scans that have a crazy red cast using GIMP (you can also suggest other free software tho).

The problem i am facing is not the color correction itself but rather the loss of contrast in the extremely dark and extremely bright areas.

Here's what i've done but i am not completely happy.

Spoiler

This is the original photo:

and this is my edit:

as you can see the detail in the sky, in the forest on the top right and on the suit on the bottom left guy are completely gone.

How can i remove the red cast without destroying the contrast? I want an easy way, like moving 2-3 sliders until it looks somewhat good, i don't want to have it done professionally since it's dozens of photos.

EDIT: Oh yeah, and if it's not too much work, how can i get rid of the artifacts in the sky?

EDIT2: What I did to achieve the result in the spoiler was remove red cast with "Colors -> levels -> select red -> tune until looks okay" and then increase exposure to 1 to brighten it up a little.

Skiiwee29 · January 1, 2022

I don't know the answers to your questions, but wanted to say that's a damn good correction IMO from what you had to work with!

FloRolf · January 1, 2022

9 minutes ago, Skiiwee29 said:

I don't know the answers to your questions, but wanted to say that's a damn good correction IMO from what you had to work with!

haha yeah thanks it's not too bad honestly

It's actually incredibly easy with gimp, learning how to do it and doing it took like 5 minutes total. Quite amazing what you can still get out of 60 year old pictures in such a short time.

tikker · January 1, 2022

For other software, darktable maybe? https://www.darktable.org/

I recently used it for some image correcting (well, more altering to suit my needs) and it was nice in that "drag some sliders" sense. I'm far from an expert, just hopping around between stuff to see what I can do with them for my needs and I liked this one. Plus it has non-destructive editing which is one thing I often really don't like about GIMP.

Your edit looks miles better from the original already though nontheless.

[Edit] here's what I got from messing with various sliders until it look ok in darktable (if you don't mind). Not as good as yours, I think your colours look much better, but the detail crushing seems avoidable. Maybe lowering contrast or something can achieve the same in GIMP.

FloRolf · January 1, 2022

32 minutes ago, tikker said:

For other software, darktable maybe? https://www.darktable.org/

I recently used it for some image correcting (well, more altering to suit my needs) and it was nice in that "drag some sliders" sense. I'm far from an expert, just hopping around between stuff to see what I can do with them for my needs and I liked this one. Plus it has non-destructive editing which is one thing I often really don't like about GIMP.

Your edit looks miles better from the original already though nontheless.

[Edit] here's what I got from messing with various sliders until it look ok in darktable (if you don't mind). Not as good as yours, I think your colours look much better, but the detail crushing seems avoidable. Maybe lowering contrast or something can achieve the same in GIMP.

Thanks! That doesn't look too bad either, as you said my colours are nicer but your details are better. There has to be a way

I'll check Darktable out as well, maybe i can tune it right or maybe just use both programs lol.

minibois · January 1, 2022

Photo restoration isn't really my thing, but I know some of the basics.

1 hour ago, FloRolf said:

as you can see the detail in the sky, in the forest on the top right and on the suit on the bottom left guy are completely gone.

What might work is first starting by turning the photo into grayscale (Colors > Saturation > set to 0 (drag slider to the left). Then you have a grayscale photo and you can tune the brightness levels of different parts of the image. You can edit the value levels in the image using Colors > Curves or Levels. Curves has more options to edit the grayscale and Levels is easier to use.

1 hour ago, FloRolf said:

Oh yeah, and if it's not too much work, how can i get rid of the artifacts in the sky?

Use the Clone tool (Press 'C' to select it), set the brush to a relatively blurry one (i.e. '2. Hardness 025') and then look at one of the artifacts. Hold Ctrl and click on a nearby clean (but same color) part of the image and now let go of Ctrl. If you now 'paint' on the picture, you paint with that part of the picture you Ctrl+Clicked on. Remove the artifact (remember, 'less is more', only remove the artifact and don't overdo the correction). Repeat on all the other artifacts.

For the 'stains' you see in the sky I use the smudge tool (press 'S') and selected the nearby color to smudge the stain so it fits with the picture around it

1 hour ago, FloRolf said:

What I did to achieve the result in the spoiler was remove red cast with "Colors -> levels -> select red -> tune until looks okay" and then increase exposure to 1 to brighten it up a little.

Colorizing isn't something I really know anything about, but I can shed some light on why you lost the detail in the sky/forest/suit. By using this method you sort of lose some of the detail in the darkest and lightest part of the image, as that is what the levels feature does; bring certain shades closer to each other.

The result you got is great, but you probably just have amplify the result of the dark/light parts using the original overlayed on it.

I did various effects for a test here, using the original image (in grayscale) and your colored edit. By taking a grayscale image and pasting it above your colored version and setting the grayscale layer to "Merge" and setting the opacity lower, I got some detail back in the dark parts of the image.

Taking another grayscale layer - set to Darken Only, with 50% opacity - I brought back some detail in the sky of the image.

After that, I did a couple more edits (i.e. saturation and darkening the image a bit again), I got this:

Spoiler

(I did the clone tool "artifact remove" and smudge tool "stain remove" things too)

Definitely not perfect, but that brought back some detail in the sky and dark parts. Might give some inspiration on what you could try next!

Your edit already looks really great!

FloRolf · January 1, 2022

53 minutes ago, minibois said:

Photo restoration isn't really my thing, but I know some of the basics.

What might work is first starting by turning the photo into grayscale (Colors > Saturation > set to 0 (drag slider to the left). Then you have a grayscale photo and you can tune the brightness levels of different parts of the image. You can edit the value levels in the image using Colors > Curves or Levels. Curves has more options to edit the grayscale and Levels is easier to use.

Use the Clone tool (Press 'C' to select it), set the brush to a relatively blurry one (i.e. '2. Hardness 025') and then look at one of the artifacts. Hold Ctrl and click on a nearby clean (but same color) part of the image and now let go of Ctrl. If you now 'paint' on the picture, you paint with that part of the picture you Ctrl+Clicked on. Remove the artifact (remember, 'less is more', only remove the artifact and don't overdo the correction). Repeat on all the other artifacts.

For the 'stains' you see in the sky I use the smudge tool (press 'S') and selected the nearby color to smudge the stain so it fits with the picture around it

Colorizing isn't something I really know anything about, but I can shed some light on why you lost the detail in the sky/forest/suit. By using this method you sort of lose some of the detail in the darkest and lightest part of the image, as that is what the levels feature does; bring certain shades closer to each other.

The result you got is great, but you probably just have amplify the result of the dark/light parts using the original overlayed on it.

I did various effects for a test here, using the original image (in grayscale) and your colored edit. By taking a grayscale image and pasting it above your colored version and setting the grayscale layer to "Merge" and setting the opacity lower, I got some detail back in the dark parts of the image.

Taking another grayscale layer - set to Darken Only, with 50% opacity - I brought back some detail in the sky of the image.

After that, I did a couple more edits (i.e. saturation and darkening the image a bit again), I got this:

Hide contents

(I did the clone tool "artifact remove" and smudge tool "stain remove" things too)

Definitely not perfect, but that brought back some detail in the sky and dark parts. Might give some inspiration on what you could try next!

Your edit already looks really great!

wow nice that looks amazing! You wanna do 50 more?

I honestly hate Photo Editing because i really don't know how all that layering stuff actually works but it seems to produce good results so i might have to look into it!

Smudge removale seems easy though, i guess i do that first right, so that it goes through all the greyscale layers etc?

Do you mind sending me the full size version of your edit? I think i'll use that!

minibois · January 1, 2022

5 hours ago, FloRolf said:

You wanna do 50 more?

Hey hey, you did all the legwork by providing a colorized version, I just edited based upon that!

5 hours ago, FloRolf said:

I honestly hate Photo Editing because i really don't know how all that layering stuff actually works but it seems to produce good results so i might have to look into it!

Smudge removale seems easy though, i guess i do that first right, so that it goes through all the greyscale layers etc?

Doing the clean up (i.e. artifact/smudges) is best to do at first, that way everytime you'd copy the layer, that stuff transfers with it (plus, any small mishaps with the removal of that stuff is 'covered up' by some of the edits made later)

5 hours ago, FloRolf said:

Do you mind sending me the full size version of your edit? I think i'll use that!

I've attached the .xcf (GIMP) file below. I have removed some less important layers, but kept the most important ones (and gave them hopefully useful names).

Some layers have a different mode and opacity, to change their effect on below layers and generally change the effect of that effect.

ColorizedPhotoEdit.xcf

WannaMurderMicrosoft · January 13, 2022

Use the healing tool for the artifacts in the sky.

If you want a fast way out of it use sky replacement.

I use lightroom or photoshop.

Pictures have limitations on how much they can be edited. That depends on the original quality.

An obvious mistake that you have done is that you have crushed the whites.

This is as good as it gets in my opinion.

ToniOnline · January 13, 2022

Hi, I learned to do digital Photo editing on Photoshop years ago, however I am no expert, and am just getting back into it as family members have asked for help. I would suggest that your colour correction of the red colour space is too much causing the loss of details in the trousers and other areas, this often happens with auto corrections. I will tell you what I did in Photoshop and you can see if it works for you I am not sure exactly how it translates to other programs but hopefully with be of some use.

I created a Levels adjustment layer and left the setting as RGB (so all the colours would be altered at the same time) I then used the grey selection tool and clicked on the grey concrete pipes. I often find the grey colour selection tool gives an easier colour correction than Black or white in most instances. The immediate change is attached as image 1 Levels. Most people would be happy with this, however I always do a further tweak. I add another level adjustment layer and then select each colour Red, Green then Blue and crop the sliders and move the middle slider (mid-tones) to further refine the colours, I feel this improved the colours of the sky especially, though also increased the obvious watermarks.

This is just with a very quick/basic levels adjustment, I have not touched colours, contrast, exposure or damage from watermarks or scratches. The other question is how the original image was digitised and from what as that also plays a huge roll in what can be done. For instance if the original was from a slide there can be a lot more data obtained, also sometimes using digital ICE while scanning can help a lot with the scratches etc though this again depends on what is used to scan the image.

I have in the past removed watermarks, I will have a play with the image in the next few days to remember how I did it.