Selective White Balance Adjustment in an Image

[williamr15724395]

 A little help understanding. Once I import an image, open the basic panel, it gives me an option to set WB to a specific Kelvin. Once that occurs, you can no longer set kelvin, only make adjustments to the slider.  Why is there no option to set kelvin as in C1 for example?

The claim is that LR hard bakes the WB at the first and that future adjustments made with the slider are color adjustments stacked on top of the original WB (as evidenced by the fact there is no option for kelvin). Is that correct, or does LR use the underlying raw image data to make that adjustment?

[Rob_Cullen]

I cannot reproduce what you describe in my Version 9.0.   When editing a RAW file the Color panel allows me to change WB between Default presets, Slider, or enter a Kelvin number, at any time when editing a raw file.

If the image is not RAW then the number can only be changed -100<>+100.

Are you editing a RAW file? What is C1?

[Conrad_C]

I can think of two reasons why you might not be seeing Kelvin.

Rob_Cullen already covered one reason: If it isn’t a raw file, you don’t get an absolute Kelvin scale but a relative -100 to +100 scale.

But that doesn’t explain why you might see Kelvin for the first adjustment but not for a later one. For that, I have to ask if you are creating masks. That’s because masks don’t use Kelvin for white balance, they are relative to the white balance set for the entire image. So you can set a raw image to 6500K, and then you create any mask, then the Temperature value range for that mask will be -100 to +100. Could that explain what you are seeing?

One thing is for sure: The way it works is totally self-consistent, in other words you won’t see the scale change for a certain type of edit:

• If it’s a raw file, the Temperature scale for the entire image is always Kelvin. This remains true for images I go back to when the last edit was years ago, it never just switches to -100 to +100.  
• If it isn’t a raw file,  the Temperature scale for the entire image is always relative -100 to +100. 
• If it’s a mask, the Temperature scale for the mask is always relative -100 to +100. When you exit the mask and return to the entire image, the Temperature scale once again depends on whether that image is or isn’t raw. So if you exit the mask and it’s a raw file, the Temperature scale goes back to Kelvin.

[williamr15724395]

To be clear I'm working from s raw file. If I understand the responses correctly, LR allows you to set the initial WB using Kelvin, but when you go to a mask, it apparently stacks a color adjustment +/- on top of the original WB setting.

Question 1- why isn't there an option to set WB adjustments (in a mask) to a specific Kelvin?

Question 2 - is the WB adjustment (in a mask) an adjustment based off the raw file data, or is it merely a color shift?

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[JohanElzenga]

White balance in a mask can't be set to Kelvin, because it is an additional adjustment. The general white balance of a raw image is not an adjustment, but a setting. In the editing pipeline you set the adjustment using the global sliders, and then you can make local changes to that using masks.

[williamr15724395]

So to clarify your comment, additional WB changes in a mask are color shifts (not based on raw data) stacked on top of a base WB setting?

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[JohanElzenga]

Yes. You can compare a mask with a layer. The base image has the white balance set in degrees Kelvin. A raw file has no white balance yet (technically a raw file is greyscale, because it only has one value per pixel rather than three), so the white balance needs to be set upon raw conversion. The 'as shot' value is just a metadata entry that is read by Lightroom as a starting point. A mask is like a layer, so a white balance adjustment in a mask is a color shift that is put on top of the base image.

[Conrad_C]

So to clarify your comment, additional WB changes in a mask are color shifts (not based on raw data) stacked on top of a base WB setting?
By @williamr15724395

In other words, they work the same as any other masked adjustment. At least my understanding is that all masked adjustments are relative to the image-wide settings. 

I just tested this. I added a Radial Gradient mask with an Exposure +1 adjustment to one image, then copied and pasted that mask to a different image at the same position. I then compared the values at the center of the mask in both images. The values were very different, and the Point Curve Targeted Adjustment Tool shows that tonal level of the same pixel location to be at very different places in the histogram in each image. That seems to prove that the mask of Exposure +1 does not set the masked area to an absolute Exposure +1 value in both images, it offsets the current Exposure value of those pixels by +1 relative to each image’s current image-wide setting.

Now, is that right or wrong?

In traditional photographic terms, how Lightroom Classic applies a mask is 100% consistent with what analog film photographers expect when masking (dudging and burning) in a traditional chemical darkroom. In the darkroom, a straight print is whatever the values are across the film. When using a mask to dodge or burn, or when applying contrast or color filtration in the enlarger, the result is a shift relative to those original film values. That’s exactly what Adobe does.

It’s also how Photoshop adjustment layers such as Levels, Curves, and Color Balance work.

So I have to think that Adobe designed Photoshop/Lightroom/Camera Raw masks to work in the way that they knew traditional photographers would expect. For those historical reasons, it’s very likely that other photo editing software works the same way.

[visual_Echo3201]

Thank you. The reason for my question came up as a discussion between myself and a friend who uses "another" software which does allow you to set WB as Kelvin in a mask, which according to him provides a more precise setting than the sliders or eye dropper for that matter. Both stack adjustments on a base WB, but the "other" seems (per his examples) to provide a more consistent color. 

I need to go back to him now with a better explanation on how Adobe does it, and let him come up with "his brands" method.