White Balance using Curves

[KeithRJ (Keith - Perth, Australia - Win11, PL8, VP3, Canon, DJI)]

Hi all,

I thought I would share two images with their .DOP files to illustrate how to correct White Balance using my curves technique.

I have two images, one a RAW file and the other a JPG file. These are both original files and have been taken underwater in natural light. These photos are difficult photos which show extreme incorrect WB so that I can illustrate my method of correcting WB using curves. All files are in a zip file included is this post. Please install the original image and the DOP file to that you can see what I have done with the curves.

It must be noted that JPG files are very difficult to correct in PL due to limited WB control.

First the RAW file.

This is an export with only my default preset applied (no WB)

This image has a very green/blue cast. Note the histogram.

RAW WB using eye dropper on the fish’s chin

This gives a pretty good WB and now note the histogram and see that the individual RGB channels are now all aligned.

WB using curves

Note the histogram and the Red channel in the curves tool. This is very close to how the RAW WB works.

Same as the curves WB but with some other edits to improve the image.

So, using curves to correct RAW WB is very similar to the eye dropper or adjusting the sliders. You can get a very good WB by simply watching the histogram while moving sliders. The advantage of curves is you can tweak the different sections of the curve for much finer control in the highs, mids and lows of the image. You can also adjust the individual RBG curves.

Now on the the JPG.

This is an export with only my default preset applied (no WB)

This image also has a very green/blue cast. Note the histogram.

The JPG WB adjustments just don’t give a decent WB and the dropper is very hit and miss.

WB using curves

Note that I have changed the Red and Green channels and that the histogram peaks now line up.

Same as the curves WB but with some other edits to improve the image.

In summary, you can achieve a good WB using curves for both RAW and JPG files simply by adjusting the RGB channels in the curves tool while watching the histogram and lining up the peaks. This technique is particularly good for JPG files which are much more difficult to WB than RAW files.

I have attached a zip files with all the files required for you to practice with. The DOP files has a number of Virtual Copies to compare the curves technique with the WB tool as illustrated above.

I hope you find this short tutorial useful for those difficult photos such and underwater and artificial lights such as club and disco scenes.

WB_with_Curves.zip (28.1 MB)

[George]

It seems you try to create BW images.

George

[KeithRJ (Keith - Perth, Australia - Win11, PL8, VP3, Canon, DJI)]

@George

It seems you try to create BW images.

No, the definition of the histogram is the graphing of the number of pixels at each brightness level. All I am doing is lining up the channels so the number of pixels for each curve match. Colour is maintained because the peaks can have different heights giving you your colour.

[George]

@KeithRJ

You can also adjust the individual RBG curves. Note also that adjusting single channels do affect the others so you will have to jump between the channels to reach your final WB.

When adjusting the red channel by example the blue and green channel don’t change. The others, RGB and L, are made out of the combination of the 3 colour. So they change when adjusting one or more colors.

There are not much colors in your image. The channels are all nearby in the individual pixels. Using the pipet will place these channels even coser to each other resulting in a grey picture. And overlapping colors in your histogram.

George

[KeithRJ (Keith - Perth, Australia - Win11, PL8, VP3, Canon, DJI)]

I will post a more colourful pic to illustrate that it works for all photos. It just happens the pics I chose are of pretty monochrome fish but the colour is true to what they are in real life.

[KeithRJ (Keith - Perth, Australia - Win11, PL8, VP3, Canon, DJI)]

Here is another example but this time with a colourful fish to illustrate I am not converting to B&W. The zip file with original, dop and export of the final image is below.

Original with just my default profile.

Histogram

White balanced with curves

Histogram

My curves

Files to play with
IMG_0972.zip (6.4 MB)

[Oldjstein ([5800X, RTX3090, 32GB DDR4, WIN10, Z72])]

Since you first described this in another thread, I’ve been trying it out with numerous random images, and like the WB picker, it works sometimes well and other times not so good. It’s a good option to have. If you subsequently choose B&W rendering, however, your custom RGB curves will be applied to the monochrome image with the resulting color cast. It doesn’t really matter to me, because for monochrome conversions I would export to Silver Efex rather than convert and edit in PL.

[George]

Your zip file doesn’t contain the raw.
Strange that if I create a vc of the master and reset that all kind of function stay active. Reset doesn’t work on this and maybe others/all jpg.
Did you start with a jpg?
But anyway if your goal is to archive similar shapes in the histogram of the channels with the use of the tone curve, then you try to get a monochrome image.
WB correction is meant to correct the results of a non-white illumination of the subject. Best way is to use the pipet on a gray background. Sand is supposed to be about gray.
I think this correction is not always desired. Think about sunset/rise. But also underwater images. It doesn’t do the feeling any good.

George

[George]

I just found that preset for RGB was set on in PL8. Not by me.
Anyway this is the jpg with everything off.

And this with wb correction based on the sand.

And then with some exposure correction.

George

[KeithRJ (Keith - Perth, Australia - Win11, PL8, VP3, Canon, DJI)]

@George

Your zip file doesn’t contain the raw.

The original is a JPG so no raw file. Jpg images are the most difficult because WB only provides Warmth slider.

Using sand for the picker is not an option here because the sand on Ningaloo Reef is slightly red.

I understand that you can get a reasonable WB using the picker but it is never correct unless you have a grey card with you. I have to adjust these pics by eye to get the colour correct for the fish and this is a method I stumbled upon and works for all my underwater photos which I have published in a book. It is very important to me to get the colour right.

Your final image is washed out and should have a little more red in it

[George]

@KeithRJ

Your final image is washed out and should have a little more red in it

That’s why I wrote

@George

I think this correction is not always desired. Think about sunset/rise. But also underwater images. It doesn’t do the feeling any good.

WB can only be done on the raw image. It influences the used parameters in the demosaicing proces. The results are pixels containing 3 colors.
The histogram is showing you a statistical view of how often an individual color within a pixel is used in the image. There’s no relation between wb and histogram.

Of course you may use the curves to get a pleasant result.

George

[KeithRJ (Keith - Perth, Australia - Win11, PL8, VP3, Canon, DJI)]

@George

WB can only be done on the raw image.

Not true! PL is the only editor that only gives half the WB tools that all other programs I have ever used do. You can WB any file as it is just colour casts you are modifying.

Each photo is different and you have to treat them as such. I am not saying you must remove all colour casts and as I pointed out in my original post that sunsets etc have a colour cast due to the ambient light which is what your actually want.

[KeithRJ (Keith - Perth, Australia - Win11, PL8, VP3, Canon, DJI)]

@George

The histogram is showing you a statistical view of how often an individual color within a pixel is used in the image. There’s no relation between wb and histogram.

Again, not true! Study the definition of a histogram to get a full understanding of what it represents. WB shows very clearly in the individual channels of the histogram simply by one or more channel being brighter or darker than the others. Moving the channel right or left brightens or darkens that channel which adds our removes colour casts. The result shows very clearly in the histogram.

Also study what WB actually is and you will get a better understanding of the whole process. Any image can be balanced.

[KeithRJ (Keith - Perth, Australia - Win11, PL8, VP3, Canon, DJI)]

@George Give me any photo you have that needs WB and I will show you how the histogram can be used to help you WB it correctly.

Preferable include a grey card in the photo if you have one.

[George]

White balance or the color temperature is setting the parameters the demosaicing process is using. On the way to the definitive pixel the values are also gamma corrected.
You use just simple color correction. The result may but don’t have to be equal but it is a different process.

George

[George]

@KeithRJ

WB shows very clearly in the individual channels of the histogram simply by one or more channel being brighter or darker than the others.

No. Shoot a pure red surface. With a right wb you’ll see only the red channel. When you see other channels your illumination of that surface is done with non-white light or with a wrong color temperature.
The histogram is just a statistical presentation of the used color channels, not pixels. Again, there’s no relation between wb and the histogram.
Wb or color temperature is used to correct the non white illumination of the image or subject. Even on a red surface.

Try with this image of @Joanna
_JNA0055.NEF (15.3 MB)
or the jpg

George

[KeithRJ (Keith - Perth, Australia - Win11, PL8, VP3, Canon, DJI)]

That picture is already correct so nothing needs to be done!

[George]

How can you tell from the histogram?

George

[KeithRJ (Keith - Perth, Australia - Win11, PL8, VP3, Canon, DJI)]

@George

How can you tell from the histogram?

Your don’t need to! Look at the picture and you can see it is fine, the sky is the correct blue so changing WB would “break” the picture.

You need to evaluated the picture to see if the WB needs changing!