Originally posted by d.bradley I still cannot understand all the fuzz about.
Obviously, circle of confusion diameters are proportional to aperture which is
defined to be f/x.
So, if a, b are the sizes of confusion circles at at f/4 and f/5.6, respectively, one gets
b = a *4/5.6 = 0.714 a
Taking the measure, the DA is fine whereas A has wrong aperture f/4.7, not f/5.6!
Why this is so, we can only speculate.... (I guess it is an AF error).
And of course, the size of the circle of confusion only depends on focal length, aperture, and distances to in-focus and out-of-focus subjects.
Bokeh, as it is used now in English and German language, seems to mean the rendition quality at a given size of circle of confusion, which is primarily determined by out-of-focus CA and shape/number of aperture blades.