How to remove blue cast from shadows?

cloudwrangler · Dec 1, 2023

I underdeveloped my film so there's an uneven blue tone in my shadows.

I tried changing the hue and temperature of the area but it comes out looking too yellow, magenta, or colorless. Any techniques for balancing it? I am using Darktable but hopefully the techniques are agnostic of platform.

Romanko · Dec 1, 2023

Use "color balance" and adjust the shadows.

Just curious what went wrong with your processing?

petrk · Dec 2, 2023

Global adjustment will not work, i think, and you are right, it will result in strange colors. Romanko gives you a good advise that can work for this image, but may not work for some others, it is still a globally aplied correction. Normaly, the blue cast of shadow is natural, because the light source for this part of image comes from the blue sky only. But if you feel it should be corrected, I would simply desaturate the shadow part a bit. In Photoshop, Gimp, Affinity etc I would use a mask to isolate the shadow part and adjust it after.

Philippe-Georges · Dec 2, 2023

Normally I would have used a Wratten 1A or a Wratten 81C Colour Correction Filter on the camera's lens while shooting this kind of scene.

But I doubt that it would have been of any use in the example you showed, as under developing disturbs the colour balance rather seriously...
Correcting this, after scanning, in P.S. will be rather difficult, if not impossible.
And if I am not mistaking (and I hardly recall), there is somewhere a function in P.S., in the 'Filters' section I think, where these Colour Correcting Filters are present, but I have to admit not having (thoroughly-) used P.S. for ages.
That is why I referred to these filters as they exist in P.S. too, and this could be of any help in digital post processing your photo...
Only some trial and error will show if this would savage this image, but, perhaps, you can convert it into B&W?

PS: a Wratten 1A is sometimes called a "Sky-Light" filter, which is easy to find used.

Romanko · Dec 2, 2023

cloudwrangler said:
underdeveloped my film

Also, what film is it, how it was scanned and what did you use to invert it? In Negadoctor you can adjust the white balance of your highlights and shadows. In most cases this works quite well.

Bruce Williams made a good tutorial on using Negadoctor in Darktable.

koraks · Dec 2, 2023

cloudwrangler said:
Any techniques for balancing it?

Adjust the blue curve, but limit it to the shadows only. This is the lower part of the curve.
Because there's a hint of a green cast left after adjusting the blue curve, I did the same to the green curve as well.

Obviously, there's a lot going on in the colors of that image that's likely beyond repair, so it's never going to look stellar:
* There's an overall cyan cast
* There's a more pronounced cyan cast in a vertical band along the right edge of the frame; it's also associated with lower density in the positive image (lighter overall tone)
* There's crossover with magenta/yellow highlights
It looks like not just underdevelopment, but also uneven development or uneven illumination during digitization.

If you're worried about the blue patch in the shadow of the building all the way to the right edge of the frame, keep in mind that this is to a large extent a natural reflection of the blue sky, and to a small extent exaggerated by the local cyan cast I mentioned above.

guangong · Dec 2, 2023

Shadows are bluish. When viewing shadows our brain automatically makes a color correction. When painting shadows, a little bluishness is added. As I see it, nothing wrong with film or processing, but simply records what IT sees.

koraks · Dec 2, 2023

guangong said:
Shadows are bluish.

True.

guangong said:
As I see it, nothing wrong with film or processing,

Can't say if it's the processing, but *something* really is not right with that image, color-wise. Whether it's development or some digital artefact, I don't know.

Alan Edward Klein · Dec 2, 2023

I clicked on Auto adjust color in my Adobe Elements program.

koraks · Dec 2, 2023

Alan Edward Klein said:
I clicked on Auto adjust color in my Adobe Elements program.

This has successfully introduced a yellow cast on top of the existing color problems of the frame.
It shows that Adobe Elements cannot substitute for human color balancing.

Alan Edward Klein · Dec 2, 2023

koraks said:
This has successfully introduced a yellow cast on top of the existing color problems of the frame.
It shows that Adobe Elements cannot substitute for human color balancing.

There are many other manual adjustments I could have made. But I wanted to show that a simple auto adjustment could do a lot of the main work. Also, I was working from his edited photo rather than the original which is a hard and inefficient way to do it. He was using Darktable which I know nothing about. Had he been using Elements, as I did, he probably would have been able to adjust it himself.

wiltw · Dec 2, 2023

koraks said:
This has successfully introduced a yellow cast on top of the existing color problems of the frame.
It shows that Adobe Elements cannot substitute for human color balancing.

I just took a copy of OP photo and find that the posted shot simply has strong yellowish content, even with as neutral a White Balance setting as I could manually set!
The trees in background, for example, exhibit that content. When I try to increase color saturation, the foliage can be see to transition from yellowish to the blue side as one slides the WB control, with little of the expected 'green' one assumes. The photo balance (color, exposure, saturation) is pretty out of kilter and hard to correct, even if one tries to segment the correction for different tonal areas...the improper development is apparent!

Here is photo with WB setting to top portion of flag pole, with increased (exaggerated) Saturation of color in order to exhibit the high yellow content of the photo

guangong · Dec 2, 2023

koraks said:
True.

Can't say if it's the processing, but *something* really is not right with that image, color-wise. Whether it's development or some digital artefact, I don't know.

Having worked with computers since the days of Sputnik, I try to avoid the digital world as much as possible in my twilight years. This is not a value judgment regarding digital, just a personal choice.

BMbikerider · Dec 2, 2023

'Blue' in sky or more or less anywhere else is very rarely actually blue. I use PS and it is very very easy to eliminate it or at least make it is not so noticeable by selectively desaturating Cyan not Blue.

Alan Edward Klein · Dec 2, 2023

cloudwrangler said:
I underdeveloped my film so there's an uneven blue tone in my shadows.

I tried changing the hue and temperature of the area but it comes out looking too yellow, magenta, or colorless. Any techniques for balancing it? I am using Darktable but hopefully the techniques are agnostic of platform.

View attachment 355314

I don;t know if anyone's asked so I'll ask. What type of film? Color negative or chrome? How did you scan? Flat or with adjustments? It;s best to scan flat and post that file here.

koraks · Dec 2, 2023

Alan Edward Klein said:
But I wanted to show that a simple auto adjustment could do a lot of the main work

I find that this route usually will get you apparently closer in one step, but it becomes much more difficult to filter out the remaining issues because they're partly masked behind a complex and nontransparent set of adjustments that were done in a black box fashion.

So in my experience, it ultimately works better to do it by visually analyzing the problem and then attacking it specifically with an appropriate manual adjustment.of course, this requires some experience, but this only is acquired by trying it. I myself have never learned anything about how color balancing works by unleashing any automatic algorithm. Experimenting with specific curve adjustments and analyzing their effects, however, I've always found more useful.

This is not to say that automatic corrections can't be useful. By all means, indulge. But personally, I've never had much luck applying solutions without understanding the problem first.

Vaughn · Dec 2, 2023

Best solution -- retake it or move on after a good learning experience.

Alan Edward Klein · Dec 2, 2023

koraks said:
I find that this route usually will get you apparently closer in one step, but it becomes much more difficult to filter out the remaining issues because they're partly masked behind a complex and nontransparent set of adjustments that were done in a black box fashion.

So in my experience, it ultimately works better to do it by visually analyzing the problem and then attacking it specifically with an appropriate manual adjustment.of course, this requires some experience, but this only is acquired by trying it. I myself have never learned anything about how color balancing works by unleashing any automatic algorithm. Experimenting with specific curve adjustments and analyzing their effects, however, I've always found more useful.

This is not to say that automatic corrections can't be useful. By all means, indulge. But personally, I've never had much luck applying solutions without understanding the problem first.

Why don't you show us how you do it?

koraks · Dec 2, 2023

Alan Edward Klein said:
Why don't you show us how you do it?

I already did. Post #6 addresses the question OP asked and shows my approach to it. I've also posted several similar examples in comparable cases both here on the forum and on my blog.

Alan Edward Klein · Dec 3, 2023

koraks said:
I already did. Post #6 addresses the question OP asked and shows my approach to it. I've also posted several similar examples in comparable cases both here on the forum and on my blog.

I think my sample is better than yours.

koraks · Dec 3, 2023

Alan Edward Klein said:
I think my sample is better than yours.

My intent was to address specifically how to adjust a local color balance issue in the shadows, since that was the question asked.

If I were to balance the overall image in an attempt to make something presentable out of it, it would turn out something like this:

Or, if the problematic cyan-cast band on the right should be fixed, a layered approach would have to be used with a partially masked adjustment layer on top:

The problem of course remains that the color balance of this image is so fundamentally twisted that there's no reasonable way to salvage it. Both attempts above I believe are miles beyond the bland, yellow mess that the auto-color gizmo churned out, which actually is not an improvement of the original at all - just a variation that's equally problematic, taken into a different direction.

Of course, one could run the image through a selection of auto-adjustment tools and then pray for something useful to come up. It's a bit like the monkeys and the typewriters; if the N is big enough, you'll surely get something, at some point.

Alan Edward Klein · Dec 3, 2023

Your final looks better and I agree we need the original, pre-edited scan to do a better job.

koraks · Dec 3, 2023

Alan Edward Klein said:
we need the original, pre-edited scan to do a better job.

Yes, that too. Preferably before it's inverted and in any case with no clipping on any of the color channels.

cloudwrangler · Dec 12, 2023

guangong said:
Shadows are bluish. When viewing shadows our brain automatically makes a color correction. When painting shadows, a little bluishness is added. As I see it, nothing wrong with film or processing, but simply records what IT sees.

This is really interesting, thank you for the share. Sometimes I wonder if we try to fix things that are only "natural" to us after all ...

cloudwrangler · Dec 12, 2023

Alan Edward Klein said:
I don;t know if anyone's asked so I'll ask. What type of film? Color negative or chrome? How did you scan? Flat or with adjustments? It;s best to scan flat and post that file here.

Sorry for the late reply. It's Kodak Gold 200. Scanned flat I believe, though I had the local shop do it.

Here's the original unedited shot. Disappointing that the typical golden color is now greenish and seems like it messed with the cyan/blue tones.

How to remove blue cast from shadows?

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