Its definitely tricky - my original attempt was similar to your result. I learnt alot by borrowing ideas from the other forum members. Thanks for your demo.
The most difficult I find is where the sky is a mass of clouds. The difference & range of intensity can be quite large. I spent my lunch hour yesterday walking around a park next to the Thames taking pot-shots of random objects and the sky. With the idea of learning more about exposure bracketing +/- 1.0 EV and then Darktable processing.
Though, now I see there are two scenarios where I will have to have some tools in the toolbox to deal with.
- RAW overexposed (sensor clipping).
- Processed pixel clipping (don’t know if it has an exact name).
After the input and ideas from others above - I think I have at least a handle on how to deal with a situation where the sensor has clipped a little (like my original question).
I now have questions on how to cope with Processed pixel clipping - which may have been initiated by sensor clipping or just the processing pipeline.
I have a few photos with the overcast sky from yesterday that don’t have sensor clipping - but clip to white when processed. I will search the forum to see if there are similar discussions - if not I will start one on: “how people hide or disguise process clipping - especially sun through clouds”.
The scene-referred part of pipeline does not clip, it is unbounded.
Of the tone mappers, filmic clips according to your instructions: you set the white relative exposure (relative to middle grey). You can use the auto-picker, but also choose manually. You may get clipping if the curve’s contrast is too high, but you get a warning about it.
The other main tone mapper, sigmoid, never actually clips, it converges to 1 asymptotically.
In the display-referred part, after the tone mappers, you may get clipping if you overdo things. In that case, if the clipping is unwanted, reduce contrast or exposure.
The tone equalizer can help by compressing the dynamic range, while maintaining local contrast – but it may lead to halos, so be careful. You can tune the mask to eliminate the halo. Alternatively, use masked exposure corrections.
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Thanks for the pointers. I will have a play.
I agree with Kofa that Sigmoid doesn’t clip and can be a very intuitive module to use after a bit of practice.
With filmic I often just use the auto tune levels and more than 90% of the time I am happy with where the white and black relative exposure slides are set. There are some images where auto tune levels looks terrible. This is very much the case when the scene is low contrast and contains no whites or blacks.
I no longer ever use the processing pixel clipping indicator and even very rarely do I use the histogram. This were vital tools in Adobe’s programs but since Sigmoid and filmic are both capable of preventing undesirable clipping I just judge the image by the look. I may wanting clipping of certain highlights such as the sun on a chrome bumper bar, or I may want pure blacks with a silhouette.
But the raw clipping is the problem we want to avoid. Reconstructing blown highlights is not easy or fun.
I agree too, but with the proviso that so much detail can be lost in the compression of really bright bits that it can almost look like it’s clipped - tone eq is the solution 
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I think this is key… I recall one photo presented here one time and it was just a shocker…it was a fuji image and it was almost black to start with and you could just make out the sky… Adding 3 or 4 EV made it look amazing and there was not a massive problem with noise and the sky was nicely intact… I recall several forum members were similarly impressed. That may be extreme but the new cameras are really getting good and I suspect in many cases if the sky is important then protecting if from the start should be paramount and the rest of the image will be easier to recover than trying to recreate or cover-up a blown out sky. If not possible with a single exposure then brackets where possible and if not that crop it or sky swap it… 
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It seems this is usually with the black relative calculations… usually the white seems pretty good. The black can often easily go to crushed or to 16EV at times so it usually will require an adjustment to taste IME anyway…
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That was when I first got introduced to the concept of ISO invariant sensors. I believe the fuji sensor in question you could raise the ISO value post shooting from 100 ISO to 1600ISO with no compromise to noise. Hopefully more sensors will become like that in the future and then the ETTR idea will be very much challenged.
In some ways setting the shoulders to safe in filmic seems to fend that off with even quite extreme contrast settings. I think this feature was likely inspired by the sigmoid curve. Certainly the orange indicators go away even at extreme contrast… but not likely that smooth fade to white you get with sigmoid… I still find myself sticking with filmic I just seem to feel like I have more control with highlight detail and contrast… I guess sigmoid might be better for other aspects of the edit and then you can use the tone eq or other tools to try to recover the highlights
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It would be nice if Sigmoid also had a similar ‘base development’.
I feel Sigmoid already has that base development. Set the exposure correctly in the exposure module and in Sigmoid play with the skew slider. The preserve hue slider only sometimes needs lowering if strange stuff happens in blown highlights.
Sometime I prefer filmic and some times sigmoid. They are different and give a different look. Worth the experimentation and the read of the manual. It took me a while to warm to using sigmoid, but now I often consider using it.
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Ya its a different approach to applying the curve. Its going to fade to “black and white” every time and the contrast and saturation mostly of the midtones is handled with the 3 sliders. I recall Jandren one saying that maybe 50% might actually be a good spot for a default color preservation but that was early days and looks like 100% was the decided value for that slider…
When you’re shooting in these situations you’re better off metering for the sky, I’m usually 99% in ESP/Matrix/etc and point towards the biggest sky patch. and set it to 1/3 or 1/2 stop overexpose. Usually I can still recover the sky and bring up the shadows of the foreground with no issues.
I find the color preservation slider has no effect on most images presumably because it is not needed. But setting it to zero can sometimes really help with funny colors in blown highlights. Every image is individual. I find there are three different options I have processing images. My default is filmic V6, second choice is Sigmoid and third choice is filmic V5. Which is best in my eyes depends on the individual image.
Thanks for the pointers. The initial frustrations and then the ongoing discussions and demonstrations has certainly challenged me with regards to changing the way I take photos. Definitely food for thought.
Up until recently - the cameras I used could only meter center frame - so it was point at the object I wanted to be exposed - exposure hold and then recompose. The new camera which I’ve only had since end of last year can meter on the focus point but only in Evaluative mode. So it is a biased average of the whole frame. Which I have found doesn’t always result in what I might expect.
More playing, experimentation and experience needed.
From my experimentation the other day - which I mentioned above taking photos at lunch of the Thames on a 6-7 Oktas day.
There is quite a difference between Sigmoid and filmic.
Tweaked Sigmoid was used for this - all other steps were the same. To try to dull the very bright white and fade to sky - tried a blue tint - a mask & colour correction to push the brightest white with a blue tint.
Tweaked filmic was used for this - all other steps were the same as above.
Auto filmic was used for this - the processed pixel clipping has large blocks just above the tree that went to pure white. Used the mask & colour correction to add a blue tint which seemed to work by fading gradually from cloud to white.
Tweaked filmic was used for this. This was the hardest as the processing pixel clipping hole in the sky was obvious. filmic was able to blur it out a bit.
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When using filmic the default for the curve shoulders and thus contrast over the years has gone from hard to the introduction of safe and now back to hard but in the case of this image with the sky and on my monitor the trees along the river are crushed a bit…here is your edit…note the histogram pushed to extremes across parts of the image … just changing it to safe in this case I chose that for both the upper and lower end of the range brings it back in nicely and then you can further tweak the look of the sky to your taste with more range than if it is left pushed unless that is what you are looking for…
vs
EDIT
If you pull it back a bit as I mentioned you can further tweak…eg I have a preset I used in the past called clouds which is a large scale contrast bump
It gives you something like this…
So basically your edit with small change to filmic and little bump to the clouds…
Edit2
Seemed a bit color full. I had cranked up the extreme highlight saturation in filmic… back to default…none added or taken away… …but maybe something in between might acutally be nice
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I think you see it most on flowers, sunsets, the usual suspects… and also switching to ratio in those circumstances shows the range of what you can get with sigmoid with that slider or the optional mode…