Struggling to white balance an image (Darktable)

[PD1 (PD)]

In the end, the best white balance would be if we could recreate the colours as seen in natural conditions. So, instead of getting lost in technical adjustments, I decided to look at what the yellow iris looks like from alternate sites. The best representation I found was this - photo courtesy naturscape

So using this as a reference, I tried to build the flower and came up with this

Is this what it looked like when you took the photo?
DSC_0022.NEF.xmp (12.7 KB)

[kofa (István Kovács)]

To be honest, I hardly ever use it, as there are simpler tools (such as color zones or, in the new versions, color equalizer), or one could use the colour shifts in color balance rgb and apply a mask so only certain areas are modified. I find that way easier than channel mixer – but that’s only me, and there are people like @s7habo , for whom it’s second nature.

[priort (Todd Prior)]

To me that photo has a big cast as well… but I think its the greens esp with foliage…

I often find them too yellow and the green just too intense…

I prefer the green with more blue in it and darker…

and

or maybe to here

It likely depends on light and perhaps is not accurate but I like the separation and the look of green rather than the much more yellow green that blends in with the flowers…

[Dave22152 (Dave Goldberg)]

@priort

To me that photo has a big cast as well… but I think its the greens esp with foliage…

I often find them too yellow and the green just too intense…

I prefer the green with more blue in it and darker…

Just as aside, I’ve always struggled with getting greens to look right. Finding that point between sickly yellow and odd blue, to where the greens look vibrant and spring-like is a continual challenge for me. I’ve getting better, but it’s been a slow learning curve.

[Popanz (Uli)]

A lot of theory is now in this thread. I think that a correct WB isn’t a specific value, but a range. There is always the personal taste involved. Using a grey card on a sunset is pointless in my opinion, even so in theory that’s the way to achieve a correct WB. On this specific picture, you have different lighting, which makes it even harder. So you have to decide in which direction to run.

A further suggestion from a person who loves bright and warm colours:

DSC_0022.NEF.xmp (14.9 KB)

[xpatUSA (Ted Cousins)]

@PD1

I decided to look at what the yellow iris looks like from alternate sites.

Agreed.

Knowing what the subject should measure/look like is half the battle.

As to grass, I asked my new friend:

what is the correct RGB color for grass in daylight?

@ChatGPT:

The RGB color for grass in daylight can vary, but a common representation is:

Red: 124
Green: 252
Blue: 0

and for the yellow iris:

@ChatGPT:

The RGB color for a yellow iris flower typically falls in the following range:

Red: 255
Green: 215
Blue: 0

This provides a rich, golden yellow color often seen in yellow iris flowers.

[Dave22152 (Dave Goldberg)]

@Popanz

Using a grey card on a sunset is pointless in my opinion, even so in theory that’s the way to achieve a correct WB.

And in many cases it produces wrong results. I remember a video with a mountain where the snow was lit orange at sunrise, and the host showed that applying a WB correction would ruin the photo by neutralizing the color from the ice, and threw off the colors in the rest of the photo.

I try to use WB to place colors where I expect them to be, and then apply other corrections to bring the rest of the image in line with the scene. But this becomes a real challenge for me if I’m dealing with extreme lighting with overpowering color casts.

[Dave22152 (Dave Goldberg)]

@thehatterman

Say input red is 135. It goes through the channel mixer using whatever values you end up setting for the r g b sliders of the output red channel, and red comes out as 178. Why not just increase red to 178? Honestly, I am not understanding why is has to be a mixture.

With 9 sliders across 3 channels there are an infinite amount of ways that the matrix can be set, and it is just not intuitive to me. It isn’t. I cannot seem to grasp the concept.

Everyones contribution to this conversation has been absolutely brilliant, but I concede. I will stick with basic WB, it will have to be good enough.

Here’s a brief video that might help (hopefully this loads ok). This is the sunflower photo that’s been used a lot in play raws and tutorials. I made a point selection on the sky and then adjusted the blue input slider for each color channel. Note that the waveform histogram shows placement of red, green and blue.

You can see how the sky changes color with each adjustment and also how placement of the RGB lines shift on the histogram. You should also see that the yellow flower and green foliage don’t change as much because the blue input slider has less effect on those colors. This allows you to “tune” the sky colors to your liking. You can then go back and do the same thing for the greens and yellows.

[xpatUSA (Ted Cousins)]

@Dave22152

@Popanz

Using a grey card on a sunset is pointless in my opinion, even so in theory that’s the way to achieve a correct WB.

And in many cases it produces wrong results. I remember a video with a mountain where the snow was lit orange at sunrise, and the host showed that applying a WB correction would ruin the photo by neutralizing the color from the ice, and threw off the colors in the rest of the photo.

Seems like the host was presenting the overly-simple view i.e. that snow or anything white appears as white to the human eye, no matter what the lighting.

In the Real World, the degree of adaptation is more variable than that, as is the required degree of WB correction.

Hopefully, the said host would then have “backed off” the WB to make the color appearance of the snow on-screen the same as that seen by the eye on-scene …

[Dave22152 (Dave Goldberg)]

@xpatUSA

Seems like the host was presenting the overly-simple view i.e. that snow or anything white appears as white to the human eye, no matter what the lighting.

I might not have been clear that he was trying to demonstrate that this was a common error as a lead in to the rest of his tutorial.

[xpatUSA (Ted Cousins)]

@Dave22152

@xpatUSA

Seems like the host was presenting the overly-simple view i.e. that snow or anything white appears as white to the human eye, no matter what the lighting.

Hopefully, the said host would then have “backed off” the WB to make the color appearance of the snow on-screen the same as that seen by the eye on-scene …

I might not have been clear that he was trying to demonstrate that this was a common error as a lead in to the rest of his tutorial.

Ah, that makes more sense, thanks!

[xpatUSA (Ted Cousins)]

@kofa

Or, the Fuji XT-5 matrix:

		<ColorMatrices>
			<ColorMatrix planes="3">
				<ColorMatrixRow plane="0">11809 -5358 -1141</ColorMatrixRow>
				<ColorMatrixRow plane="1">-4248 12164 2343</ColorMatrixRow>
				<ColorMatrixRow plane="2">-514 1097 5848</ColorMatrixRow>
			</ColorMatrix>
		</ColorMatrices>

Dividing those by 16384 (just a guess):

  0.72076, -0.327026, -0.06964
 -0.259277, 0.74243,   0.14301
 -0.031372, 0.06696,   0.35693

Interesting … is that raw-to-XYZ?

Quite a big negative coefficient at top row middle, and quite low at bottom right.

[kofa (István Kovács)]

@xpatUSA

Interesting … is that raw-to-XYZ?

I believe yes; that’s the one used as the ‘connector space’ in most conversions.

[thehatterman]

@kofa

However, you could say: ‘decrease red where there is also green

That makes sense, that got through to me.

[thehatterman]

OK, beginning to understand. Need to play around with a few more photos, but I can get the idea that (intuitively) I am increasing/decreasing one colour where another colour is present, and the effect is greater when the other colour has a greater presence. And this is per pixel, so the effect will be different on different parts of the photo.

So like you have all said, I can see how this can lead to a bit of tug-of-war between colours. And I need to become somewhat familiar with colour, to get a feel at a quick glance as to which primaries are involved i.e. yellow is green and red with little blue for example.

It’s starting to make sense ( at bloody last I hear you shout !!)

[xpatUSA (Ted Cousins)]

@thehatterman

So like you have all said, I can see how this can lead to a bit of tug-of-war between colours. And I need to become somewhat familiar with colour, to get a feel at a quick glance as to which primaries are involved i.e. yellow is green and red with little blue for example.

It’s starting to make sense

Good to hear !

… ( at bloody last I hear you shout !!)

[Zbyma72age]

My - fun in GIMP

[thehatterman]

I have learned a lot more from this discussion than I expected. Been playing with the channel mixer more and it is coming together, albeit the case that it is a slow process for me. I do get how it works now and think I will use this tool sparingly, probably for colour cast correction as oppossed to anything artistic.

What has surprised me the most is what I think I have learned about colour. While getting the colour ‘correct’ is a technical endeavour, it has become very clear to me that the final look of the photo is completely at the whim of the artist.

[priort (Todd Prior)]

I think that @s7habo Boris just commented in another post that he was going to make extensive use of the channel mixer for an artistic style in his next video so maybe watch out for that …he has an older video where he worked up a Kodachrome style but that might have been more with rgb CB module …I would have to go back and review how he assembled it…

[paperdigits (Mica)]

@thehatterman

it has become very clear to me that the final look of the photo is completely at the whim of the artist.

Indeed! Trying to get “real” or “correct” colors where it isn’t necessary is boring!