David Goldfarb
Well-known
I agree that some people become much too obsessed with bokeh, and that it is only one interesting characteristic of lenses among many. People who use tele-wide zooms, for instance, probably don't care very much about barrel/pincushion distortion, but I do, so I only own one such lens and am very careful about the situations in which I use it.
On the other hand, I think that concern about the rendering of the out of focus image was a very important thing during the Pictorialist era. Lens catalogs and advertisements of the era of soft-focus lenses talk about disturbing double lines and other artifacts in the out of focus area long before anyone used the word "bokeh" in photography. An ad for the Wollensak Verito cited in the back of Weston's _Daybooks_ (v. 1, if I remember correctly) reads--
"a specially designed double lens... which, while it gives the desired diffused or soft optical effect, shows no distortion, double lines, or other optical imperfections, and being rectilinear gives an even diffusion over the whole plate... Will not make sharp negatives with wiry definition unless stopped down to f:8."
"double lines, or other optical imperfections" in this context means "bad bokeh." A Verito achieves its diffuse focus effect with uncorrected spherical aberration from wide open to about f:8, after which you can still see some chromatic aberration, which would not have been so much of a problem in the age of ortho plates.
Somewhere in the 1960s, I think, this was forgotten, and resolution and cost became the only factors driving the market for lenses, so you could overcorrect for spherical aberration to improve sharpness at the expense of smooth bokeh and sell more lenses, because no one worried about the out-of-focus image, or you could offer the convenience of a reasonably sharp tele-wide zoom at the expense of barrel/pincushion distortion at the extremes and sell more lenses that way, because most people aren't worried about distortion. Of course there are zooms for motion picture cameras that are both sharp and have relatively low distortion, but at astronomical cost.
On the other hand, I think that concern about the rendering of the out of focus image was a very important thing during the Pictorialist era. Lens catalogs and advertisements of the era of soft-focus lenses talk about disturbing double lines and other artifacts in the out of focus area long before anyone used the word "bokeh" in photography. An ad for the Wollensak Verito cited in the back of Weston's _Daybooks_ (v. 1, if I remember correctly) reads--
"a specially designed double lens... which, while it gives the desired diffused or soft optical effect, shows no distortion, double lines, or other optical imperfections, and being rectilinear gives an even diffusion over the whole plate... Will not make sharp negatives with wiry definition unless stopped down to f:8."
"double lines, or other optical imperfections" in this context means "bad bokeh." A Verito achieves its diffuse focus effect with uncorrected spherical aberration from wide open to about f:8, after which you can still see some chromatic aberration, which would not have been so much of a problem in the age of ortho plates.
Somewhere in the 1960s, I think, this was forgotten, and resolution and cost became the only factors driving the market for lenses, so you could overcorrect for spherical aberration to improve sharpness at the expense of smooth bokeh and sell more lenses, because no one worried about the out-of-focus image, or you could offer the convenience of a reasonably sharp tele-wide zoom at the expense of barrel/pincushion distortion at the extremes and sell more lenses that way, because most people aren't worried about distortion. Of course there are zooms for motion picture cameras that are both sharp and have relatively low distortion, but at astronomical cost.
