Hello Everyone,
I've remembered that in older version of Lightroom the Parametric Curves have had the modified Point Curve displayed as a 'baseline' for modifications instead of the default linear curve. So by using the parametric curve sliders, we directly modified the already adjusted Point Curve and got immediate visual feedback of it. This was viewed as a bug and was fixed accordingly.
On the last comment in the linked thread it's said that:
'Note that this was a bug in the display of the Parameteric Curve, not in how the actual slider settings were interpreted.'
However, I disagree with the last few words. To this day, it seems to be the way the Parametric Curve is interpreted.
In a quick experiement I've created a black to white gradient, then lowered the white point to 60 with the Point Curve.
This puts even the brightest parts of the image into the Shadows section of the Parametric Curve.
However, when I adjust the Parametric Curve, I can only affect the brightest parts of the image with the Highlights slider, even tho they are now technically in the shadows. This means the Parametric Curve works relative to the Point Curve and interprets the newly set white point as 'pure white', then makes it's adjustments accordingly.
With this behavior, I believe that seeing the changes in the Point Curve when adjusting the Parametric Curve was a feature, not a bug, as it gives a useful visual representation of what areas will be affected by our changes.
That being said, not having the modified Point Curve visible is a perfectly fine design choice as well, especially how the RGB Curves effects would still not be visually shown. So the current one might even be a better design, as the Point Curve now serves as a master curve, and the Parametric Curve works only within the constraints of the new baseline, set by the Point Curve. It makes full sense, however it breaks consistency, because the RGB Curves does not see the Point Curve as a master curve (unlike in Photoshop) and their range will not be constrained by it. (And I personally wish it was, wish if the RGB Curves worked with the same logic as the Parametric Curves does)
Now we have two features of the same tool visually matching, but under the hood doing very different things. Let me show an example.
As said before, I've created a pure black to pure white gradient, then moved the white point to 60:
Using the parametric curve, I can affect the new 'highlight' area by using the Highlights Slider. Keep an on the shape of the curve:
If I reset the slider and try to recreate a similar shape in all the RGB channels, I would expect the same behavior, however, for the RGB curves, the areas in the highlights are already invisible, as there are no longer highlights on the photo once it was modified by the Point Curve. Because of this, adjusting the highlight area has no effect on the image at all, it's enought to just look at the histogram if it's not immediately visible:
This has some consequences. One is the inconsistency within the tool itself. Visually we have 2 matching curves, but depending on which curve is used, they affect the image differently, without this difference being communicated to the user. By having the Point Curve shown as a base for the Parametric Curve, this used to be solved before.
Also, from what I see in Photoshop, the Point Curve sets the white and black point for all RGB channels, so for example I cannot add color to the lowered white point, only remove from it. It seems like the RGB Curves are working only within the restrictions of the Point Curve. In Lightroom it's not done and because of that, a chunk of the RGB curves are 'wasted' if the image is faded by the Point Curve. So now we have areas of the RGB curves that does nothing, no matter the modifications we make as long as they are anchored to that area only.
And this also have another possibly undesireable effect. Depending on the style, we would often want to keep whites as whites and blacks as black without any color cast to them, even when faded. If the Point Curve restricted the RGB Curves, then by keeping the black and white points at their default positions on the RGB channels, we could always guarantee that we don't spill any color to the blacks and whites no matter what other modifications we make in those channels.
However, if they are not relative to the Point Curve, but absolute on their own, we need to carefully anchor the new black and white points to avoid color spills and modify it each time they are changed in the Point Curves.
To demonstrate this, I've lowered the white point to mid grey (125), then applied an agressive curve in the red curve channel. In Photoshop this keps my newly set black and white points intact:
In Lightroom however, the new white point was not seen as whites by the red curve and it added color to it:
In order to keep my whites netural, I need to put an anchor to the same point on the red channel where my white point was set on the Point Curve. After doing that and working left from said point I can recrate the same behavior as seen in Photoshop. However, now the whole right half of my curves are useless:
As far as I can see the advantage of this logic is that it's now possible to add color to the faded whites, not just removing them (same just the opposite goes for blacks). It's fairly flexible as I can increase the exposure with the RGB curves as well with no limits.
But in my view, it makes working with curves harder. They are much more sensitive, as now the useful area we have is smaller, so we can't make the same gradual adjustments when extreme fades are introduced. I would personally expect to set the limits of my image in the Point Curves, then color grade within the constraints of it only using the RGB channels. It would also make it easy to keep blacks and whites netural if needed.
What do you guys think about this all? Do you prefer Photoshop's or Lightroom's curves?
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