What about a picker tool for the curves to allow to modify the luminance of the “picked” part of the image.
Something that some other softwares are proposing.
Please describe how that should work - so that we can better understand what you mean…
It could put a dot of the curve to see where to modify
A Click in the image will show the respective point on the curve?
Pickup circle with user defined size?
We could go a step further: make it work like Lightrooms colour tools? Click and drag up or down to change the values?
Reminds me of u-points, augmented with variable selectivity…
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A picker tool should also work with the HSL color wheel, to show where in the color wheel the average color around the picker is located.
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A picker tool should also work with the HSL color wheel
That would be perfect for night sky photography. I’ve been killing glow coming over the horizon by selecting the exact color of the glow (very narrow band on the wheel) and killing luminance and saturation. But finding the exact color is kind of a PITA - a picker would help.
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Friends, that’s already in the backlog and was addressed in another votable topic:
Perhaps the present discussion should stay focused on the curves tool. 
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Good point! Glad to see a HSL picker is “on the list”.
As someone who’s used Photoshop for a few decades, it would be nice to have three pickers. Go have a look at PS to see what I mean (high, mid, low). Useful for manual color correction.
Although I have to admit, the ‘this is neutral’ color picker on the ‘color’ panel does an good job - even if the neutral is night sky.
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Yes, I would like a picker for the tone curve. Like in LR or PS, it’s quick & easy to adjust the tone curve / Gradationskurve – and a good starting point for editing.
have fun, Wolfgang
My ulimate exposure toolset would be a exposureslider which i can set as we have now.
Plus a blacklevel marker and a whitepoint marker.
Use 1, ETTR or ETTL. Not automated average but pull to the ground or push to the ceiling kind of picker.
Use 2, mark both and get a kind of stretched exposure line. A not smart lighting kind of Dynamic Range placement.
An other thing i am very keen on having in DxO is a connection of the graphics of the tonecurve and the contrast and tone controls.
A visualisation of the changes i make in selective tone and contrast advanged contrast.
Gamma can be connected to the exposure section.
It may be a seperate window or a embedded image in the tonecurve tool.
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Affinity Photo (and likely the other Affinity apps) has an interesting UI for this: drag-able lines right on the histogram, drag WP and BP lines in from the right and left, respectively. I can’t really speak to its usability as I’m an AP noob - but it looks good.
Well, that’s how to set black / white level in PL’s Tone Curve tool – move the ‘corner points’ inwards and control with shadow / highlight clipping warnings activated in the Histogram.
( even better / quicker, if there was a histogram in the Tone Curve tool – like AP … ).
Similar to the HSL tool, adding a picker in Tone Curve tool allows to quickly grab any value from the picture, one intends to lighten / darken, and set the additional anchor points automatically, without any guessing – a good starting point for editing.
have fun, Wolfgang
Agreed that it’s trivial to set WP and BP in the tone curve - that’s how PS (and LR?) work. And yes, agreed, I, too would like a tone picker, the way it works in PS (point moves up and down the curve as you move it around the image. (in earlier versions of PS, I used to use this with the RGB tools to sort color casts, and, very occasionally, do split toning).
That said, I found the AP UI for this (which also has a tone curve, BTW) interesting, probably easier for some folks to visualize.
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Just to add my perception of the feature as I see it and how it could/should be implemented.
I note that this threads last comment was over 2 years…hopefully a refresh and DxO team insight/comment might be forthcoming?
In the Tone Curve controls ~ a picker to select a point on the image that would place a fix on the curve line. This function ideally needs to allow for picking multiple points on the image so that when adjusting the curve, specific slight changes can be made to the Tone Curve based on those chosen points in the image.
TIA 
PS for more control ~ right clicking on a point on the curve allows its deletion/reset, if required rather than resetting the whole curve
PPS it was @platypus that pointed out to me that I was posting a similar ‘feature request’ here
Tone Curve…more nuanced control(s) - DxO PhotoLab / Which feature do you need? - DxO Forums
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Indeed.
Pickers should be present everywhere relevant.
Like in this case.
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