On the subject of Depth of Field/"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".

Now, if for you, the "soft focus optical effect, no distortion, double lines, or other optical imperfections, and... even diffusion over the whole plate" is precisely a promotion of bokeh construction lens, for me it's even more precisely a characterization of - a soft focus lens, known to the lens designers for a long time and constructed as such. Bokeh lens design? Are all bokeh constructed lenses soft focus lenses?? Or do they have some characteristics on their own, known to the lens designers and designed especially for this "bokeh" effect?
I think what you try to sell as bokeh is something else...

[Oren Grad]

Actually, make that the 'teens - go to the Camera Eccentric website, open page 12 of the Wollensak catalog from 1912-13, and you'll find the passage from which David has quoted in earlier threads on the topic here.

The quote demonstrates that by the 1910s:

* double-line rendering, which is specifically an effect that occurs outside the plane of focus, and thus a bokeh effect, was recognized as a defect
* a particular lens design optimized for portrait use was valued in part for its ability to avoid double-line rendering
* a manufacturer had chosen to promote its product on that basis

Double line imperfection = bokeh as to when in the Japanese literature??

I don't know when the various flavors of bokeh first began to be cited as such in the Japanese literature, but it's not material to my point.

[GPS]

Actually, make that the 'teens - go to the Camera Eccentric website, open page 12 of the Wollensak catalog from 1912-13, and you'll find the passage from which David has quoted in earlier threads on the topic here.

The quote demonstrates that by the 1910s:

* double-line rendering, which is specifically an effect that occurs outside the plane of focus, and thus a bokeh effect, was recognized as a defect
* a particular lens design optimized for portrait use was valued in part for its ability to avoid double-line rendering
* a manufacturer had chosen to promote its product on that basis

I don't know when the various flavors of bokeh first began to be cited as such in the Japanese literature, but it's not material to my point.

While it is true that the double-line rendering was regarded as an imperfection the lens in question was designed as a soft focus portrait lens, not as a good bokeh lens. Again, you try to put modern aesthetic bokeh criteria on old lens design criteria.
What I say is that the characteristics the lens designers were after is a soft focus lens, not a much later Japanese bokeh elusive description. That came as a side effect.
A soft focus lens and a bokeh lens design is not the same if the bokeh mania came much much later than the desired design.
The Mediterranean diet didn't come on tables because of the modern anti cancer diet exigences.

[GPS]

Actually, make that the 'teens - go to the Camera Eccentric website, open page 12 of the Wollensak catalog from 1912-13, and you'll find the passage from which David has quoted in earlier threads on the topic here.

The quote demonstrates that by the 1910s:

* double-line rendering, which is specifically an effect that occurs outside the plane of focus, and thus a bokeh effect, was recognized as a defect
* a particular lens design optimized for portrait use was valued in part for its ability to avoid double-line rendering
* a manufacturer had chosen to promote its product on that basis



I don't know when the various flavors of bokeh first began to be cited as such in the Japanese literature, but it's not material to my point.

Do you know any old lens that is not a soft focus lens but designed so that it could avoid the "double-line rendering" thus having this desired bokeh effect?? Never heard of it in the lens design literature...

[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

The quote demonstrates that Wollensak did that.

suggesting that this lens was designed especially for this magic.

This part remains speculation, at least based on the evidence at hand. My sense is that, over the years, most designers, for most lenses, have optimized for performance in the plane of focus and let the OOF chips fall where they may.

In recent years among small-format lenses, there have been a handful designed specifically with bokeh in mind. The obvious examples are the 105 and 135 AF DC Nikkors, which are not soft-focus lenses; the DC ring is specifically a bokeh control. Beyond that, manufacturers have moved to more circular iris designs even in lenses with optical designs that clearly have not been optimized for pleasing bokeh.

[GPS]

The quote demonstrates that Wollensak did that.



This part remains speculation, at least based on the evidence at hand. My sense is that, over the years, most designers, for most lenses, have optimized for performance in the plane of focus and let the chips fall where they may.

In recent years among small-format lenses, there have been a handful designed specifically with bokeh in mind. The obvious examples are the 105 and 135 AF DC Nikkors, which are not soft-focus lenses; the DC ring is specifically a bokeh control. Beyond that, manufacturers have moved to more circular iris designs even in lenses with optical designs that clearly have not been optimized for pleasing bokeh.

No, Wollensak does not mention the modern pleasing bokeh. Bokeh is not the same as a soft focus lens description.

Recent lens design does not enter in the specific discussion of the old lens design. Let's not displace the discussion...
Of course, it's well known that the modern bokeh mania was used in the modern lens descriptions and designs. It has no bearing on the old lens design exigences. Romans didn't invent their diet because of today's cancer research...

[Oren Grad]

No, Wollensak does not mention the modern pleasing bokeh. Bokeh is not the same as a soft focus lens description.

The argument, simply, is that double-line rendering is necessarily a property of the out of focus part of the image, and therefore that Wollensak had to have been aware of OOF character as an attribute distinct from plane-of-focus character because they explicitly cited a phenomenon that does not appear in the plane of focus.

That's all.

[Paul Fitzgerald]

"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."

I doubt it, precision machining and manufacturing would off-set any material savings from the brass, AND/OR they could have expanded the aperture shell like B&L and others.

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

No, the old manufacturers knew exactly what they wanted and worked for it, it's only the word 'bokeh' that's new to the scene. Read the old literature from Dallmeyer, TTH Cooke, Voightlander, Goerz, Steinheil, B&L and Wollensak.

One other thought, 'back in the day' these big dogs cost a year's salary or more, any obvious cost-cutting would not have been accepted.

[Walter Calahan]

"I dare to say, the new-time lens designers are not less smart physical scientists. They too understand the issues..."

But management tell the engineers to cut cost so they use fewer blades.

[Lachlan 717]

"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."

I doubt it, precision machining and manufacturing would off-set any material savings from the brass, AND/OR they could have expanded the aperture shell like B&L and others.

I think that you have missed my point. I was not talking about "material savings" per se; reduced depth of each blade allowed a reduced-diameter aperture shell, reducing weight. I am suggesting that they purposely avoided expanding the aperture shell to save weight

No, the old manufacturers knew exactly what they wanted and worked for it, it's only the word 'bokeh' that's new to the scene. Read the old literature from Dallmeyer, TTH Cooke, Voightlander, Goerz, Steinheil, B&L and Wollensak.

As I wasn't there, I am not going to be categoric in my assumption of their intent. I would hope that, unless you're 100+ years old and discussed this exact point with the lens' designers, you would not assume to know either.

One other thought, 'back in the day' these big dogs cost a year's salary or more, any obvious cost-cutting would not have been accepted.

Why not? It still happens all of the time in high end manufacturing today. Why did they go with brass? Why not gold plate it to prevent it from tarnishing? Simple: cost. Simple business theory says that you make your product as cheaply as the intended market will accept so as to maximise your margin whilst maximising your client base.

Anyway, back to the topic. Perhaps it needs to be explained why multi-bladed apertures were brought in when a Waterhouse stop can provide a near perfect circle. I have no idea. So much for Occam’s Razor…