I’ll try to explain my former post.
One editing window and 2 images. The histogram or waveform is showing the pixel values of the whole editing window. The x-axis showing pixel values in the histogram and showing columns in the waveform. Changing the brightness in image 1 will cause an overall change in the histogram but a selective change in the waveform.
George
I forgot the image
Vision: Select a place in the wave display and drag it up or down to brighten or darken the respective area = graphical variable/selective tone adjustment. Add selection size and feather sliders if wanted.
I’m not trying to be argumentative; I just want to get to the bottom of what benefit a waveform would bring.
But isn’t that only going affect a vertical “stripe” of the image? Why wouldn’t I use a straightforward Local Adjustment?
And, in using any type of adjustment, we tend to judge the effect on the image, not ont he appearance of a histogram or waveform - don’t we?
That’s why we need the size/feather sliders
…well, I was trying to make the diagram useful 
With apologies @Joanna, you have sounded to this reader rather argumentative in this thread. If you “just want to get to the bottom of what benefit a waveform would bring” during PL editing, why not simply ask that question as your original post ? Sorry if I have misunderstood what you have been trying to say.
In your posts you have also sounded as though you yourself don’t use a histogram in editing. Fine. But why do you then have such strong views that the option of a waveform would/should not be helpful to other PL users (who may, or may not, not use the PL histogram themselves) ?
IMO a waveform in PL would be helpful, ie. to me, in my workflow, in select circumstances. I sometimes export an image into Affinity during post-processing with PL simply to get this analysis of it. I find it most relevant when colour grading and when the image has marked differences in both tones and colours between the subject(s) and background. I think this is similar to the use case the OP demonstrated.
FWIW, it gets my vote as a desirable feature, with the caveat expressed by the OP and others that it be an alternative, not a replacement, for the existing histogram on which some users rely.
You can see which parts of the image you want to expose for. As an example, if you have a backlit subject you can use the waveform to see the exposure of your subject and ignore the blown highlights of the background. The video in DPReview referenced in the original post explains this.
Exactly. Unless your subject fills a substantial part of the frame the histogram basically shows you the levels in your background. Not in your subject. (See my example of the dancer.)
The waveform shows you histograms of slices…. So you can see in a chart how your subject is exposed. (See the histogram of the narrow slice. And then the waveform back in the original post.
I understand that but, if they are vertical slices, how do I use it to evaluate “exposure” for a horizontal feature?
Before processing…
After processing just by using the Spot Measure Smart Lighting, the Tone Curve and a tad of Colour Wheel…
You don’t even use a histogram so I don’t really know why you’re asking the question.
It’s true that I’ve sometimes wanted to be able to switch the vertically sliced waveform to a horizontally sliced waveform but we don’t even have a traditional vertical waveform here.
Most of my photography is fundamentally of people. So a vertical waveform is better in general for me.
Can I ask why you feel it necessary to rely on anything other than the image to judge how you want to edit an image?
Surely, it is what the image looks like to the eye that matters, not whether it can be analysed in stripes, slices, or other artificial partitions?
OK, here I go again, harping back to the “good old days” of film but, looking at the work of the “pre-waveform”, or even “pre-histogram” photographers, makes me wonder how on earth they managed to get such good results 
Because sometimes I want to make sure my eyes aren’t deceiving me. I edit in many situations and in many environments. While I do have a calibrated laptop screen, I can’t always control the lighting in the room where I’m editing.
Anyway really this thread doesn’t apply to you since you don’t use the histogram. Can you imagine the uproar if DXO didn’t have a histogram capability?
It’s interesting because there are many features in Photolab that I don’t use… and I can’t imagine a use for. But if someone else suggests an improvement to one of those features I don’t feel the need to tell them they’re “doing it wrong. Who uses that.”
If someone suggests an improvement to “miniature effect”, I just go to the next post…
@MikeR, plainly a histogram shouldn’t/doesn’t change with rotation of the image. But with a waveform, you can (temporarily) rotate an image 90° within the editor (eg. if using Affinity in the absence of the feature from PL) in order to see the waveform as applied to horizontal slices, if relevant to that particular image.
I would propose that any PL implementation either incorporates re-calculation of the waveform upon a rotation of the image (either the original or a VC) in this way, or perhaps allows rotation of this new tool’s application to the image in its original orientation (I’ve no idea how ‘easy’ the latter would be to perform).
That’s true and reminds me that on occasion I have rotated video just to see the waveform of the horizontal axis. And sometimes zoomed in also for easier grading.
And yes of course the waveform needs to take into account rotation, zoom, and all adjustments really.
Actually, as I have mentioned elsewhere, I do occasionally look at the histogram; usually to determine if there is any room to expand the tonal range in the case of a “flat” subject. I just don’t use it to judge an image since, as the saying goes, a picture is worth a thousand words.
I’m not saying anyone is “doing it wrong”, just that there are a whole load of other things that DxO could be implementing - like making all adjustments available as local as well as global.
Now, if someone suggests removing it, that would definitely get my vote.
So, I repeat my previous question that nobody has yet answered…
After all, if you want a feature, it might be a good idea to justify exactly what tool you would be able to use better with the “waveform” that is not possible presently.
I thought some would be obvious:
The obvious ones are any that you may look at a histogram for like:
Contrast
Exposure Comp
Selective Tone
Curves, etc.
But in addition waveforms can help you with:
Vignetting
White balance
And local adjustments
If you really want to understand, download Davinci resolve, Learn a bit how to use it, add some images to a timeline, switch over to the color editor and start making adjustments.
This is really what the user interface should be anyway. Adjustments show on the image instantly as well as instantaneous updating of the waveform. There are no rendering delays. It’s fantastic and what I eventually hope for with DXO as adjustments are made.
Please excuse my insistence but, what would I do differently from how I do it now?
Surely, in making all of these adjustments, my final guide has to be how the whole image appears.
Why don’t you put up a couple of screenshots to explain how you would decide on how much of one of these adjustments to make, based on the waveform instead of the image?
Not having the time to download and learn enough about DaVinci Resolve, I did take a look at a video on YouTube.
So, it’s primarily a video editing suite and the guy on the video demonstrating the waveform seemed to be mainly using it for scene matching. Except, despite all his fiddling around with the waveform, he still kept on saying that the final decision should be made by looking at the image.
It certainly seems a busy interface and I assume it suits video editing, although I also noticed that there are all sorts of control knob/slider hardware accessories to ease keeping tabs on everything.
As for rendering delays, it’s not something I notice any problem with in PL.
That is a question only you can answer. Seriously this isn’t for you. You can safely move along with no negative impact to how you use PL today.
My question is - why would I want it, or more importantly, why would DxO spend a lot of time and money implementing it? The more votes a request gathers, the more DxO are likely to do something about it.
You need to convince hard-nut, “I’ve always managed without it” sceptics like me, who may well exist amongst the decision makers at DxO.
@Joanna, I think by now it’s pretty clear that you wouldn’t want it … and I’ve no desire to persuade you that you ever would or should. I assume you haven’t voted for it and have voted for other features that you do want. Without trying to persuade you therefore, but referring to your previous question, I would say that if you do ever use the histogram to assess “the tonal range of a flat subject”, then this feature would help you do exactly that if ever your ‘subject’ (like the ballet dancers cited by the OP) forms only a slice (vertical or horizontal, as discussed above) of the entire frame. It’s functionally an enriched histogram for a slice of the frame. One can achieve something similar by temporarily cropping the frame to leave just that slice and looking at its histogram once cropped, but one can’t then see the rest of the frame’s histogram simultaneously to assess what is happening to tonal range elsewhere under a global adjustment. If one is applying local adjustments only, then the value of the feature is reduced, but for global adjustments it offers a local analysis that the histogram can’t. My eyes may tell me whether I ‘like’ the image; this tool helps me analyse why and understand what has worked (or not as the case may be) in parts of the frame. I learn a lot by analysing my likes and dislikes and carrying the lessons forward. Other people learn differently.
I’m sure you not convinced and that’s fine by me. Nor have I any wish to convince other “hard-nut sceptics” they would or should want it. To any of DxO’s decision-makers reading this, I will say that by voting for it I have indicated it would factor into whether I choose to pay good money to upgrade to PL6 or not, rather than spending that money on the next payable upgrade to Affinity. As will other feature upgrades for which I have voted. I expect that’s what their commercial decision will be based upon and why they operate this sub-forum … unless of course they get their kicks by watching a good pointless squabble. 
The video Fix Tone & Color Using Advanced Adjustments with DxO PhotoLab 5 is online.
( demonstration about vibrancy → min 18:00 )
