Let's see your lone tree images - here is one I just shot

Yes, believe it or not, a tree:

Cool subject.

Interesting background -apparently not clouds ...

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Nope -- not clouds -- artifacts from overprocessing. 😂 I think it's the soft contrast setting that does it.

Yep, the "soft contrast" slider in Silver Efex will do this every time around edges. Unless you want the effect, you have to use soft contract gingerly. Interesting shot BTW.

I've also seen similar when using Contrast-Limited Adaptive Histogram Equalization ...

CLAHE is a pretty standard imaging processing algorithms. It was developed actually by the US military many moons ago to dig down into such things as foliage and/or camouflage to be able to detect objects hiding therein in imagery. For this application, no one cared about distortion and artifacts. They only cared about detecting and identifying tanks, trucks, airplanes, etc. It could make an image look like crap but make targets stand out. I expect the "soft contrast" slider in Silver Efex is based on versions of these algorithms.

en.wikipedia.org/wiki/Adaptive_histogram_equalization#:~:text=Contrast%20Limited%20AHE%20(CLAHE)%20is,slope%20of%20the%20transformation%20function.

Nailed it!

Usually, I back off when seeing the effect. But on this particular photo, I felt it needed the stronger processing. The artifact is much more visible at the smaller size than the larger size, at least to my eyes. In any case, I'll probably try to edit the photo in a manner to minimize the artifacts while keeping the tone. Note I did say "try". 😁

Thanks! I think the processing makes the shot, in this case. With lesser processing, it's less interesting.

In short, I've weaponized my processing. 😎

Das ein gut waffen ist ...

CLAHE slope 5, block 63, hist 256

No you just accentuated the hard edges. Automatic Target Recognition starts with accentuating edges for Automatic Edge Detection. Then after the edges are found, other processing is used to fill in the shapes and characterize man made objects to support ATR. The result of the whole processing chain is to have a computer fine some poor sucker so you can drop a bomb on his pumpkin head. Much has become the foundations in commercial image processing came out of places like the University of New Mexico Image Research Laboratory and the US National Laboratories dating back to the mid 1970's when the US started to use of digital image sensors for reconnaissance started.

The usual put-down that I have come to expect from your good self. In any case, CLAHE with the stated parameter values does NOT "just accentuate the hard edges" - any fool can do that with USM, right?

The knowledgeable history of Automatic Target Recognition is of little interest to me, sorry.

That reminded me of a tree-in-the-street shot I took years ago in Bellville, TX. The shot is long-gone and I am not well enough to go and repeat the shot. So ... Google is my friend, voila:

Mornington Peninsula, Australia

A small and daring one...

Panorama Walk, Llangollen, north Wales