See attached image for reference.
When choosing the best option, what exactly should I take into account, is it only inner smoothness, or the general object appearance, including outer walls and/or corners?
So for example, I definitely remove 20,15 and 10, but then I have no idea which one to pick.
The best inner area is 5 (glossy finish, no lines whatsoever, I can’t even feel the lines with the nail), but it has the worst corners (overextruded).
-20, on the other hand, has best corners and outer lines, but has bad inner area (no gloss, visible underextrusion).
So which one to pick? Or should I not be doing so called ‘Complete Calibration’, but do a Fine Calibration instead, lowering the Flow Rate manually?
I turn it different angles and orientations in the light and try to pick the smoothest looking one overall, not so much at the edge but inside the edge.
You are only showing the first pass here. When you do the second pass, choose the one higher than the best one, which will give you all values above and below the best, so you can refine your selection.
There are two suggestions I would make. First, use your cell phone camera to take a macro shot and blow it up on a larger computer monitor or simply zoom in. The camera is far less forgiving than the human eye. It will become very apparent which one is smoother.
The second suggested one the finger nail test. Take the back of your fingernail and rub it across the grain, this is far less subjective and you will feel a difference in texture immediately not to mention the difference in raspy noise from your finger nail.
And the third honorable mention is to use a 10X jewelers loupe. I have a couple of different varieties for my day job but the one I purchased that is designed for stamp and coin collectors is by far the best for looking at 3d prints under magnification.
BTW: 10X is all your need, I have a 30X and it is overmagnification and serves zero purpose in 3D printing other than to narrow your field of view to the point of being useless. Whereas 10X allows for a field of view large enough to see a large swatch of layers which is really what you need when inspecting prints. Add to that this loupe I linked to has a scale printed on the inside of the box which serves as both a perfect focal distance as well as a measurement tool.
