On the subject of Depth of Field/"Bokeh"

[Jim Galli]

A lot of hair splitting goes on. Bokeh is largely unquantifiable. What is it you are looking to achieve. Beautiful bokeh is an expensive and seemingly bottomless pit. Wade through my web pages for a taste. Most folk though don't see the nuances. What you've got out in front of the lens is 98% of the picture if the bokeh is 2%. Still, I've spent a lot of money and had a lovely time exploring that 2%. I'm not done yet.

[mrpengun]

It seems to me that the bokeh "story" is quite a young one. Did anybody speak about bokeh in the beginning of the 1900s?
Beside that, if it is true what Struan says (citing Merkling) does anybody think that the old-time lens designers were after a pleasing bokeh in their lens design (not in the number of aperture leaves)?? I don't think there is any mention of it in the scientific optical literature.

I would agree--my knowledge of photographic history is much stronger than my knowledge of photographic practice :-)
In terms of history, the monkey-wrench would be pictoralism. Prior to that, it can be said (over-simplified, of course) that there was a push for ever-increasing sharpness. Folk like Juliet-Margaret Cameron's portraits were part of a 'soft focus push', although in some of her letters and diaries claims to simply "have forgotten to use the fine-focus" (a paraphrase).
To that end, it is important to view the growth of photography in relationship to painting and criticism--not to mention the legal positions of printing and books (e.g. Talbot's patents on Paper-negatives for printing). Many established art institutions kept trying to push photography away by sort of 'altering the goal-posts' for its acceptance. Eventually (again, over simplifying for the sake of brevity), movements like pictoralism take hold because they show photography as an artistic craft just like any other, with many of the same skills and finished products.
In the early 20th century, Modernism and New-objectivity again promoted sharpness.

However, while we're on the subject, will tilts and swings change the affective shape of the iris? not to mention greatly affect the lens-properties with regards to DoF affects?

[rdenney]

It is subjective, to be sure, but it's not non-quantifiable. We just haven't developed a good model yet. But it would certainly be possible to do so.

Until then, and until photographers learn how to interpret such a model in terms of their own tastes, the only advice is to keep the lenses that make images one things are beautiful and sell the rest.

I've also considered this at some length. Number of aperture blades is somewhat of a shibboleth, I think, because many lenses are used wide open to maximize selective focus, and it's in the presence of extreme selective focus that people seem to care most about bokeh. All lenses have a round aperture when used wide open.

The aperture shape affects the shape of out-of-focus specular highlights. I'm not sure it's all that visible when evaluating the general character of out-of-focus blur that doesn't have such highlights, especially if the lens renders those details with a (lovely) faded edge.

I tested the bokeh of some lenses for medium and small format, and put up a web page showing the results. The worst bokeh of the lot was displayed by an old Bausch and Lomb 139mm Tessar, which like most ancient barrel lenses has at least a dozen blades and a very round aperture.

Rick "who likes his bokeh smooooooth" Denney

[Jim Galli]

It seems to me that the bokeh "story" is quite a young one. Did anybody speak about bokeh in the beginning of the 1900s?
Beside that, if it is true what Struan says (citing Merkling) does anybody think that the old-time lens designers were after a pleasing bokeh in their lens design (not in the number of aperture leaves)?? I don't think there is any mention of it in the scientific optical literature.

Just because the japanese word had not come into favor yet doesn't mean the pictorialists from a century ago were not paying a great deal of attention. Yes, I absolutely think the lens designers were after pleasing bokeh in some of their lenses, and in particular the ones intended for portraiture. The one happy accident that set the bar so to speak was the petzval lens. They were just trying to make a lens fast enough to photograph humans and damn the rest of the shortfalls. But it took no time especially in the age of anastigmats to figure out how pleasing a petzval was for portraits.

[GPS]

...

However, while we're on the subject, will tilts and swings change the affective shape of the iris? not to mention greatly affect the lens-properties with regards to DoF affects?

They won't change the effective shape of the iris (they have no mechanical effect on them , sorry, it's cheap, I know... ) - as to the affective shape, it's profoundly unknown to me...
Anyway, it will change the shape of all forms in the picture as normal tilts and swings do, it's only logical.
And the DoF effects are well known...

[Lachlan 717]

Those old-time lens designers were some pretty smart physical scientists.

It seems to me that used lots of blades, because they explored and understood the issues.

Could it be that this was not an aesthetic decision, but a weight-saving one? It seems to me that the fewer blades used, the greater their required depth to cover the full aperture distance. The more blades, the thinner the required blade.

Thus, deep blades would have required a bigger housing diameter.

Given these Ol' Boys were made from brass (not alloy/plastic), this would have resulted in significant (maybe even too much to carry and/or mount) weight increases.

So, maybe this discussion about Bokeh is the tail wagging the dog?

Lachlan

[GPS]

Just because the japanese word had not come into favor yet doesn't mean the pictorialists from a century ago were not paying a great deal of attention. Yes, I absolutely think the lens designers were after pleasing bokeh in some of their lenses, and in particular the ones intended for portraiture. The one happy accident that set the bar so to speak was the petzval lens. They were just trying to make a lens fast enough to photograph humans and damn the rest of the shortfalls. But it took no time especially in the age of anastigmats to figure out how pleasing a petzval was for portraits.

Wait a moment, not so quickly..! You cannot exchange the cause for the effect. Petzval was in no way after pleasing bokeh in the design of his lens, that's obvious!
If the pictorialists were using the out of focus shapes for their artistic expression it is not yet a reason for the lens designers to go after it in their lens design. No mention of it in the scientific optics literature. That photographers could see the difference in the "bokeh" is a totally different thing from the lens design demands. I don't think there ever was any catalog tooting their lenses as those with "pleasing bokeh" or whatever the magic word could be for their lenses in the old times, suggesting that this lens was designed especially for this magic.

[Oren Grad]

I don't think there ever was any catalog tooting their lenses as those with "pleasing bokeh" or whatever the magic word could be for their lenses in the old times, suggesting that this lens was designed especially for this magic.

As David Goldfarb has pointed out previously, promotional literature for the Verito back in the 1920s made precisely such a claim:

"...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 line imperfection" is what the Japanese refer to literally as "ni-sen bokeh".

[GPS]

As David Goldfarb has pointed out previously, promotional literature for the Verito back in the 1920s made precisely such a claim:

"...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 line imperfection" is what the Japanese refer to literally as "ni-sen bokeh".

David Goldfarb where??
Soft focus = bokeh?? No distortion = bokeh? Other optical imperfections = bokeh?
Double line imperfection = bokeh as to when in the Japanese literature?? Surely not in the 1920...
Again - let's not exchange the cause for the effect, the later aesthetic criteria for the former lens design exigences.

[GPS]

As David Goldfarb has pointed out previously, promotional literature for the Verito back in the 1920s made precisely such a claim:

"...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 line imperfection" is what the Japanese refer to literally as "ni-sen bokeh".

Now, if you can come with a 1900s Japanese definition of bokeh that would be something..! For the time being, the bokeh definition is quite elusive...