Bokeh is about personal preference
it is how the image is rendered
any lens maker would design their lens differently to render differently (both in focus and out of focus)
therefore it has nothing to do with the aperture (of course you still need shallow enough DOF to express the bokeh)
some like smooth bokeh that is all blur
some like bokeh that is, while smooth, still retain the shape
but it is safe to say that people generally dislike harsh bokeh (over-correction)
as for the in focus and out focus rendering
they are in fact interrelated
so you are kinda correct to say you need to see both to decide
I know nothing about the physics of optics but as far as my experience goes, it is easier to make a sharp lens with harsh bokeh (most third party Japanese Lens makers do that, like Sigma or Tamron, most of their lenses are really sharp, sometimes sharper than the original brands, but has ugly bokeh)
whereas it is often difficult to make a sharp lens with smooth bokeh
>> Exactly people confuse bokeh with fast lens
Exactly what is bokeh? Can anyone give a comprehensible definition?
I'm not sure I know, but this is what I see that might be close to what people talked about by "bokeh".
First it's not about the rendering of the out of focus image, or how smooth the out of focus blurring.
what I like about Leica or zeiss's image, when it fits my taste, is the rendering of the in-focus image within the the out of focus background.
It's how the in-focus image smoothly stands out from the rest of the out-of-focus image. When it fits my taste, I can hardly draw the line between the in-focus elements and the out-of-focus elements. They are just integrated as an one image.
Very often I saw the review articles or magazines zooming out the out of focus background, to show how good or bad the bokeh, with no in-focus elements in the context.
Not that they are wrong, as I'm not sure exactly what is right, but something is just missing from the point.