Bokeh is a Japanese word that refers to the subjective visual impression of the out of focus areas of an image. Just because bokeh isn't objectively measurable doesn't mean it's BS, but there's certainly been a lot of BS written about it. What imaging characteristics contribute to beautiful bokeh? What kind of lenses that are most likely to be "bokeh monsters?"? Which vintage and contemporary lenses should bokeh fanatics go for? Just ask me and I'll give you my arrogant but educated opinions-
The term comes from the Japanese word boke (暈け/ボケ), which means "blur" or "haze", resulting in boke-aji (ボケ味), the "blur quality".
A definition: The quality of the blur seen in the out-of-focus portion of a photograph. The quality of bokeh is largely dependent on the construction of the lens. But it is also heavily influenced by the focus distance and the physical size of the aperture, and this latter is dependent for any given f/number on the focal length of the lens.
In general, good bokeh is considered to be smooth and pleasing, whereas "bad bokeh" is typically considered to have a jagged and discordant effect on the blur, and on the photo as a whole. Of course, one can imagine image situations where the effect desired for a given photo might prefer the "good bokeh" look just as easily as situations where the effect desired can take advantage of the "bad bokeh" look.
There are no useful metrics for bokeh.
Discussion: I have a fairly wide range of lenses that I use on APS-C, FF, and MF-D cameras, from 10mm to 360mm. Nominating any of them to being "good bokeh" or "bad bokeh" lenses is way too simplistic a way of looking at bokeh. What I usually want in an image is to allow the primary subject matter to be clearly presented and separated by sharpness, contrast, and tonal quality from other elements in the imaged space. Sometimes this is best done with using large apertures to limit the depth of field, other times it is better by framing such that the light and shadow demarcate the primary subject cleanly. Generally, any large masses of blur in the foreground are distracting from the primary subject, and jangly/blobby blurs surrounding or behind the primary subject similarly distract. With some lenses and some subjects, a wide open aperture produces exactly the bokeh I am looking for; with other subjects and intents, it does not and reducing the amount of blur by stopping down a little does a better job.
So ... "The Great Bokeh Controversy: Snare or Delusion?" seems a bit of bombast, a teaser to draw people into debate and argument. I've been making photographs for about sixty-some years now; the above discussion is how I've worked with cameras, lenses, and subjects for all this time in making photographs. The term "bokeh" came onto the scene as a quality to strive for about 15-20 of those years ago, and has always seemed to be just a faddish novelty term for discussion in these forums ... I mean, doesn't every thinking photographer see what kind of blur in their photos works well and what works poorly? Don't we all know that if we change our distance from a subject, change the focal length we're using, adjust the aperture, etc etc, we get different effects ... some of them pleasing, some of them not so much so, and that sometimes we're not looking to be "pleasing" and other times it's all that matters?
I don't think there's any controversy, snare, or delusion in "bokeh". Better time would be spent looking at photographs critically and understanding/discussing why some of them work—how the elements of equipment used, exposure settings used, sharpness, contrast, and the quality of the blurred parts of the photograph support the photographers' intents—and doing the same with other photographs that are perhaps not quite as successful in achieving the photographers' goals.
And, of course, this exercise is/would be a lot harder than just saying "a Summilux 35mm f/1.4 pre-ASPH is a bokeh monster!"
G
