Sorry I couldn’t reply to everybody. I ran out of reply credits! Anyway thanks to everybody for your inputs. I have made some good progress. Here is an edit of another photo on the same theme, from the same file. Basic edit flow was exposure, Filmic RGB, local contrast with multiply blend, and iterate a couple of times. I’ve learnt a lot about using styles to and will work on a basic style for each of the cameras used in my library.
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Great shot @Chris_Harris! You did a very good job with the processing.
However, at the edge of the photo you can see a pair of artifacts, halo and chromatic aberration.
Too much local contrast can cause halos and chromatic aberration is a problem of the lens.
Did you apply lens correction, or is your lens not supported with darktable?
Have you also tried module for chromatic aberation and defringe?
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Hi thanks for your comments. The halo was caused by the tone equaliser module I think, but maybe by local contast, I remember having to back off. The lens is unsupported and I think it would have been a Tamron 11 - 18mm that I bought for creative fun knowing that it would likely have issue. I don’t have that camera (Canon 7d) or lens anymore as they succumbed to tropical mildew at some point. Will look into the chromatic aberration module. Thanks again.
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The chromatic aberration module worked quite well. ‘defringe’ did nothing.
The halo and funny fringe nearby on the penguin’s down is caused by the “tone equaliser”. I was able to get rid of most of the halo and fringe by cranking up the ‘filter diffusion’, ‘smoothing diameter’, and ‘edges refinement/feathering’ sliders.
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Ooh, good question. In most of the tools I implement in rawproc, I hard-code a neutral default, but I didn’t with filmic. In the research I did to implement it, it was always presented as a modifier from the start, with values in the coefficients designed to do a certain off-axis shift of the curve. Conversely, the thing we think of as “gamma”, is really a simple exponential function, which if you set the exponent to 1.0. results in such a neutral default.
In rawproc, each tool has a checkbox that, if checked, tells the software to route that tool’s result image to the display. To regard filmic’s starting point, I’d just click the previous tool’s checkbox.
But, now that you’ve brought it up, in a spare moment I’ll play with my filmic tool, see if I can dial-in a set of coefficients that “straighten-out” the transfer function so X=Y. I don’t think I’ll be successful, based on the structure of the equation, but what else is there to do in solitary confinement… 
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Just ran across a good explanation by @anon41087856 for why dt’s filmic can’t have a neutral default:
Chris welcome…as you often find you need to go to the color balance module for adding back some saturations I also will use the picker to select the contrast fulcrum and use contrast in the CB module …sometimes that is all you need…obviously image dependent…
Can you elaborate on how to use the picker to select the contrast fulcrum please?
The picker can be used to select the lowest luminance that should not be darkened when applying contrast enhancement. The higher luminance range is lightened linear, the lower range are darkened with a curve.
lower area: original grayscale
upper area: increased contrast
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In most cases simply click it and it will use the entire image to determine the fulcrum
From the manual…
Thanks that is a very enlightening image 
Hmmm yes. I was wondering if you have some ‘trick’ to assess your images and choose the fulcrum point. Using the whole image will sometimes work I guess
@Chris_Harris By now you should have enough info to give it a try. Please do the processing and show us your XMP. Then we can see what can still be improved on. Heck, maybe we can learn from you. That is how our community works.
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Sorry no magic here….
_MG_9821.CR2.xmp (22.6 KB)
@Chris_Harris both are extremely nice! What do you think is the problem with them? I couldn’t find fault with the photo of the houses and the mountains, so I didn’t edit it, but I put my own spin on the boat.
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Hi thanks for that. I don’t think there was anything wrong with them in particular. The house one is a bit soft but nothing to done with that Just a couple of shots that I was using to practice with darktable. I was just responding to @afre who suggested that I post a couple of shots here for comment.
Off to have a look at your XMP file now I like that shot with the cooler colour balance too, as you have it, the version I posted was messing around with different white balances, the shot was taken very late in the day in the blue hour.
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Was totally expecting more penguin edits. Your shots are beautiful by the way.
Remember that we have a https://discuss.pixls.us/c/showcase category where you can share your finished works. 
Or https://discuss.pixls.us/c/processing/playraw where you give permission for the community to play with your images.
Hmm OK so share you sidecar file with me but how do I use it? If I replace the one in my original image directory I’ll loose my edits and history. What do you good people normal do to handle this?