torger,
What was the reason(s) for the changes you made to the example image you posted?
There's always that lazy top level reason "make things look nicer", and well, that is what I eventually fall back on, but the definition what "nice looking" is certainly not some absolute truth. Here it's important to me to not bring things too far away from realism, and that's why I like to have an a good realistic starting point (with the usual photographic limitations). The reason for that is as described I want to show the audience than an inconspicuous place or object can be turned interesting just through viewpoint and framing. So that explains why I don't make pictures to "pop" as much as possible.
I know a thing or two about color science and I'm totally aware that there is no such thing as a 100% realistic original, so I see no point in not making any post-processing at all. The overall reason to make post-processing for me is to create atmosphere, tie together images in a series and make a personal look, and it must connect back to the documentary aspect meaning that it cannot be too extreme.
I'm generally not turning too intellectual about about every post-processing modification, I do think a lot about art and there's all sorts of loose reasons flying around that shapes an aesthetic and then I do things to the image that "feels right". Especially when it comes to possible color grading, why did I add cyan rather than say yellow? I typically test through a few and pick what I like the most, and trust my intuition that if I follow that it will be good in the end. I do make the color gradings subtle, typically less than a film stock affects color. Sometimes there may be a reason to think about "warm"/"cool" tints for creating a feel/atmosphere in a more cinematic way but this image was neutral in that regard. In general my subjects are quite neutral and it's a deliberate stylistic choice I've made, my images are not so much about dramatic clearing storms or morning fog coming in and that type of stuff it's not where I've chosen to put my focus, at least not now.
Then I also have to factor in keeping a consistent style, and certainly when I present a series of images they must be processed in a similar fashion. If I present two images side by side, the grading may also be slightly affected by that to make them match better.
Changing from 4:3 to 4:5 in this particular image I think gave a clearer structure of the pine background. This is from a series I'm currently doing called "geometric chaos" (working name), and the pine background is the key "geometric" element. The vignette of 0.3 stop is a default thing in my reference look which adds depth to an image, and I always include it unless there's some particular reason not to, some images may become more graphic without a vignette, this was not one of them. In a very messy image I sometimes strengthen the vignette to make it look less messy if I think that is closer to my desired aesthetic.
The luminance contrast curve is my "clarity" tool to take down some of the fogginess originals often have. It's also a part of my consistent look, I generally use this first before I would try local contrast enhancements or clarity tricks.
Having "a reason" is in the end as fuzzy as "the message" (or rather "messages") you try to convey, it's after all art and it's supposed to be a bit fuzzy, so perhaps I was using the wrong word. Perhaps I should have instead said that I try to not post-process for "the wrong reasons", where the wrong reason is for example to make the image as likely as possible to get to 500px.com/popular (which my images really aren't suitable for anyway).