The May/June 1997 issue of Photo Techniques published three very informative articles on the matter of bokeh: “What is Bokeh?” by John Kennerdell; “Notes on the Terminology of Bokeh“ by Oren Grad; and “A Technical view of Bokeh” by Harold Merkeinger. The last article can be found posted on the internet, while the other two more interesting article are not, and are probably covered by copyright laws, so the only way to obtain them is to buy the back issue of Photo Techniques. I wish Oren Grad had decided to speak up more on the topic of bokeh, since his article is the most pertinent to this discussion. I list some of the salient points and terminology from Oren Grad‘s article:
* bokeh refers to the rendition of the out of focus areas of a photograph, and may be classified as good or bad bokeh.
* good bokeh softens the objects in front of the plane of focus (mae-boke).
*Out-of-focus background objects (ushiro-bokeh) lose detail but maintain their basis shapes and tones.
* One common fault noted in Japanese lens tests is ni-sen (two-line) bokeh: a tendency for out of focus objects to separate into two overlapping images.
* Some o-o-f highlights may be described as having enkan (ring) bokeh.
* O-o-f highlights having recognizable shapes may be described by the terms enkei (circular) bokeh, han-enjoh (semi-circular) bokeh, marumi ga aru (roundish), hosongai (long and narrow) or kometto-job
* When the lens is stopped down the blade structure of the iris may become apparent in the form of surudoi kado (sharp corners) in the ten bokeh (point bokeh)
Oren Grad’s article goes on to describe some vague and subjective bokeh terms;
* The overall look of the image may be described as sofuto (soft) or katai (hard)
* As the bokeh becomes less clean it may be described as hanzatsu (complex) or as kuzureru (breaking up or loosing shape).
Also noted in the article are some, overall judgmental terms summing up a lens’ bokeh: kirei (pretty, beautiful, clean); sunao (gentle, well behaved); yoi (good); konomashii (nice, likeable); odayaka (gentle); shzen (natural) or even “kani no yoi bokeh " - bokeh that gives a good feeling; or when the reviewer is being critical, as the absence of such qualities.
In all the first two articles noted are the most informative discussion of bokeh, and certainly more complete an explanation than I have seen anywhere on the internet.