Yeah, no. It is a thing and there are distinct differences that can quite reasonably be called "good" (smoothness) and "bad" (line-doubling due to overcorrected SA). Just because most internet discussion of it is ignorant (e.g. the fixation on aperture blade count) doesn't imply that the concept doesn't exist and/or is poorly defined.
Originally Posted by E. von Hoegh
Examples of bad "nisen" bokeh: one, two^. Note the bright rings at the outside edge of each blur-circle; these are due to overcorrection of spherical aberration and it is considered to be ugly because it creates strong features with very high spatial frequency in areas that you're trying to blur out and take the focus away from. It causes line-doubling and all sorts of distracting nastiness.
And for the opposite extreme, examples: one, two, many from the STF. Note the edges of the background highlights (first image) and how they've been dimmed out by the apodisation filter. With a normal lens, all those coloured blobs would have been sharp circular discs. When applied to an image with a less deliberately-distracting background, the apodisation filter results in extreme smoothness.
Last edited by polyglot; 04-22-2013 at 06:46 PM. Click to view previous post history.