"More" bokeh?

[Mark Sawyer]

A currently running thread contained the observation, "but my Dagor has much more bokeh than my Trigor..."

I understand the concept of bokeh as describing how the lens renders the out of focus area. But there seems to be some difference in whether it can be quantified in terms of more or less. (One example I ran across analogized saying one lens has more bokeh than another as like saying one apple has more shape than another.) On the other hand, if it is a function of spherical aberration, as quite a few sources seem to indicate, this can be measured and quantified.

I also wonder if there is any specific quality termed as "bokeh." It seems to be used to describe several different phenomenon. Sometimes it is used to refer to how small points of light are rendered, (see examples at: http://www.kenrockwell.com/tech/bokeh.htm). Sometimes it's used to talk about "swirliness" or field curvature (see figures 2 and 5 at http://www.vanwalree.com/optics/bokeh.html). Sometimes it is used to refer to how "creamy" the gradations in the highlights are...

I guess I'm trying to find out whether "bokeh" can be specifically identified and/or quantified, or if it's a generalized, undefined catch-all word for all out-of-focus rendering. Any enlightenment out there?

[David A. Goldfarb]

"More" bokeh doesn't really make sense unless you're using it in a kind of colloquial way like "a Rolls Royce is more car than I'll ever need," but you can say one lens has better or worse bokeh than another lens. I use "bokeh" to describe the rendering of the out-of-focus area of an image (actually, I prefer just to call it "out-of-focus rendering" or some such), which may include the rendering of unfocused specular highlights, lines, and anything in the out-of-focus area. The field curvature that produces the "swirliness" is particularly relevant to Petzval lenses, since most other lenses don't have such dramatic field curvature. The main cause of good or bad bokeh often seems to be over- or under-correction of spherical aberration.

People talk about specific effects like "double-line bokeh" (single lines rendered as double in the OOF area--bad), "bright ring bokeh" (specular highlights brighter at the edge of the circle of confusion than in the center--bad), the "swirly bokeh" that's been mentioned, and such. There are Japanese terms for some of these things. There is also the "plastic" or "three dimensional" effect that describes the sharp delineation of the focused area from the unfocused area, particularly characteristic of Heliars, but sometimes seen with other lenses.

[Bill_1856]

Even a well-established, simple term such as ACUTANCE may not be quantified. (Like PORN, I know it when I see it.)

[Eric Leppanen]

www.luminous-landscape.com/essays/bokeh.shtml

www.luminous-landscape.com/columns/sm-04-04-04.shtml

www.luminous-landscape.com/columns/sm-june-05.shtml

[paulr]

I think even "better" and "worse" are pretty misleading terms when it comes to bokeh (or whatever you want to call it). Looking just at spherical aberration, which is the most compelling part of the whole equation, you need to know more than good or bad. Perfectly corrected spherical aberration gives you ok looking out of focus areas. When S,A, is uncorrected in one direction, it looks really nice. In the other direction, it looks crappy.

The catch is, if it's uncorrected in the nice direction for things beyond the focal plane, it will be uncorrected in the crappy way for things closer than the focal plane. I'm seeing this now with an old (60s?) chrome barrel Hasselblad lens that I'm borrowing. Out of focus things in the distance look gorgeous. Out of focus things in the foreground look ... out of focus. I won't go as far as saying they look nasty, but there's nothing great about them.

So when you're describing a lens's bokeh, you should probably give more informatoin than more/ less or it rocks/it sucks.

[Jeffrey Sipress]

I love this word, "Bokeh". When did it originate?

After photographing for decades, reading countless books and magazines, taking classes and workshops, I only first heard it last year. Is it one of these new age phrases?

[Alan Davenport]

Ah, "The Bokeh Dialogs" are back...

It isn't possible for one lens to have "more" bokeh than any other, because bokeh refers to the subjective quality of how a lens renders objects that are out of focus. It's something that all lenses have in equal measure, and it's also something that doesn't really exist in any concrete way ("The new SharpShooter 8-2000 mm zoom's bokeh was measured at .00145.....") Bokeh can be described with terms such as smooth, harsh, creamy and crappy, but I've yet to hear of an objective criteria to categorize bokeh. We can all carry on ad infinitum about the subject without coming to any conclusion or agreement. You either like the way a lens renders the OOF areas ("good bokeh") or you hate it, as in mirror lenses for 35mm ("rotton bokeh.")

Supposedly, the term is from Japanese, with the term originally referring to persons with a few screws loose, bats in their belreys, a few cards short of a full deck. Fuzzy memory, not clear at all, etc.

[Mark Sawyer]

Jeffrey- This website (mentioned by Eric above) has the best background on the most qualified (I've seen) original source and meaning: http://www.luminous-landscape.com/columns/sm-04-04-04.shtml

I think everyone who's posted so far is right; bokeh is a quality that can be described but not quantified; like food, art, people, etc., we will sometimes disagree in terms of better or worse.

This is what I thought going in, but after seeing the original quote at the top, I googled bokeh for a while and found many references to "more bokeh," and even lens tests by people looking for the "most bokeh." I'll consider that a slight mis-use of the term, and have a litle more knowledge about the terminology now. Thanks, guys!

[Mark Sawyer]

(But the next time I take out my old Rapid Rectilinear, I'm going to sniff the lens cap like the cork of an old bottle of cabernet, say, almost to myself, "mmmmm, magnificient bokeh...")

[David A. Goldfarb]

There is an article by Merklinger that tries to describe features of "bokeh" in quantitative terms. You should be able to turn it up on the web. I think it was originally in _Photo-Techniques_. It's not a bad explanation of why things look one way or another, but the quantitative approach is like trying to describe the taste of food by looking at a chemical analysis. Of course the chemical analysis is related to the flavor, but it doesn't quite capture the subjective experience of the flavor in a way that is intuitive to most people.

Also, be aware that the critical appreciation of the appearance of the out-of-focus part of a photographic image dates at least to the era of soft-focus lenses, long before anyone used the term "bokeh" to describe it.