Saturation Doesn't Work Correctly After Tone Curve

[realspear]

Lightroom Version

12.1

Operating System

1. macOS 13 Ventura

I've found that if I use the tone curve, in particular the ones for specific colors, that the saturation doesn't work correctly. I have heavy magenta-tinted photos (from stage lighting), and I remove the tint, but then need to desaturate slightly. However, the saturation slider now only takes the image from green to magenta. If I hit the Black & White converter at the top of the adjustments panel, it just goes to green. I'd like to be able to do the color correction but slightly desaturate. The same behavior occurs with masks, I can't desaturate anything in the image.

 

[Johan Elzenga]

That sounds like perhaps you have a corrupted monitor profile, or use the wrong monitor profile. Change it temporarily to sRGB, just to see if the problem goes away.

 

[realspear]

Just tried that, happens with every profile in the system. My usual profile is from hardware calibration that I do about once a month. And that this only happens after applying the tone curve should indicate some sort of interaction inside Lightroom rather than my monitor. If I reset the tone curve, it will desaturate when I move the slider.

 

[Johan Elzenga]

Ah, I understand what you mean now. This is because of the order in which Lightroom applies adjustments. If you fully desaturate the image first, then you can color it again with curves. So the way to do this is to desaturate a bit first, and then color correct. Or perhaps use another method of color correction, like HSL or Color Grading.

 

[realspear]

Ah, I understand what you mean now. This is because of the order in which Lightroom applies adjustments. If you fully desaturate the image first, then you can color it again with curves. So the way to do this is to desaturate a bit first, and then color correct. Or perhaps use another method of color correction, like HSL or Color Grading.

That does work but the problem is that I don't know how much desaturation I need until after the color correction. I can try the others, but I've always preferred using curves for some adjustments. HSL doesn't do the type of adjustments I'm doing and Color Grading causes the same issue with the saturation slider.

 

[Johan Elzenga]

I think there is no other way. I assume that saturation is part of the demosaicing process, so that comes at the very early stage. Curves is an RGB adjustment, so that comes later in the processing stack. You can’t change that.

 

[realspear]

I think there is no other way. I assume that saturation is part of the demosaicing process, so that comes at the very early stage. Curves is an RGB adjustment, so that comes later in the processing stack. You can’t change that.

OK, thanks for the help, disappointing but that did make me think about a way to do it. First I tried Virtual Copy but that saved the adjustments rather than the adjusted image. If I export to Photoshop, it will let me either adjust saturation there, which is fine if I want to do it globally, or just immediately Save back into Lightroom, where it doesn't register the earlier adjustments, obviously. Takes more space and time but it works.

 

[bobsomrak]

@Johan Elzenga

I know there are a few thing in LrC that are order dependent now but I didn't think Tone Curves and Saturation was one of them.

 

[Johan Elzenga]

@Johan Elzenga

I know there are a few thing in LrC that are order dependent now but I didn't think Tone Curves and Saturation was one of them.

I think you are missing my point. This is not order dependent. The thing is that saturation is applied at the early stage (during demosaicing, I expect), and curves is applied later. That is the fixed order in which Lightroom Classic carries out the developing process. The user cannot influence the latter, so that means that you can turn an image B&W by setting the saturation to -100, and then add color again by using curves. This is regardless of the order in which you apply both. You will get the same result if you first apply the curve and then set saturation to -100. Try it and you will see it indeed works this way, meaning it is not order dependent (order dependent for the user, that is).

 

[bobsomrak]

@Johan Elzenga

Thanks, I did miss your point. I did the test before I posted and confirmed the behavior you state in the last post so wondered if I was missing something. Unfortunately there are a few things that are now order dependent in LrC such as Clone/Heal and a couple others I can't remember but not a big issue.

 

[Johan Elzenga]

Correct. In this case the order does not change the outcome, but it can still be useful to consider the order. The reason is that if you desaturate first and then change a color curve, you use the same order that Lightroom does and so what is happening is easier to understand than if you use curves first and desaturate after that.