Biogon == Super-Angulon? (Wikipedia says yes)

See this: http://en.wikipedia.org/wiki/Schneider_Kreuznach#Super-Angulon_2 <p>

 

Scroll down to read: <i>

 

 

These (Schneider Super/Angulons) are wide-angle lenses which have been

developed in several steps. The Super-Angulons are Biogon designs...</i><p>

 

I gotta tell you that none of my Super-Angulons look like any Biogon, nor do

they perform like a Biogon. <p>

But what do I know. I only use each regularly. Biogons are different!<p>

Or am I due for a rebrainwashing?

I don't know about this in particular, but i have to tell you something: About history, Wikipedia is sometimes WRONG, it happens, it's not really like an encyclopaedia, rather a site that collects information here and there... Yes really.

Yes, they are based on the Biogon. See Kingslake's History of Lens Design.

The Super-Angulons uses an optical trick to improve the uniformity of illumination. My understanding is that this method was invented in Russia, but became well known in the West in the Biogen, and so is frequently described in the West as the Biogen design. Lenses with this design are roughly symmetric, have large negative outer elements and smaller inner elements, given a characteristic appearence of two cones connected to a shutter. Other examples are the Grandagons and Nikkor-SWs. See page 315 of Applied Photographic Optics by Sidney F. Ray, 3rd edition, where the method is described as the Slussarev effect. Kingslake refers to a 1946 patent by Roosinov (p.150, A History of the Photographic Lens): "Roosinov found that the use of this construction had the effect of greatly increasing the oblique illumination, even out to 66 degrees from the axis, by causing an enlargement of the pupils at high obliquity angles."

I'm not going to argue with Kingslake, but the oblique exit pupil distortion effect was in use long before 1946, and in the West too. Whether it was documented and patented or not is another matter.

 

I have an early (circa 1920) Air Ministry marked aerial reconnaissance lens that clearly shows the effect. The later WWII Kodak Aero Ektar also displays the same effect, since lack of vignetting and distortion is obviously important in aerial mapping applications.

 

I believe that correcting the optical parameters that affect geometrical distortion also affects the apparent exit pupil shape across the image field, and so almost automatically leads to an improvement in illumination.

 

Incidentally, it's amazing how many posts here still quote the theoretical Cos^4 law as immutable, when clearly, there are many lens designs that contradict that "law". In fact, most of the "unbreakable" optical laws, based on the theoretical thin-lens model, aren't actually that rigid when real-life thick-lens designs are examined.

As I understand it Bertele who designed the Biogon had prevously to that designed the Aviogon for Wild Heerbrugg which he in turn based on the Russian Roosinov design. The Super Angulon was then developed from the Biogon by Schneider. So they seem to be family members rather than identical twins.

Hmm.

 

The 38/4.5 Biogon has 8 elements in 5 groups. Its front outer group consists of two air-spaced elements. Its front inner group has two cemented elements. Its rear inner group has three cemented elements. Its rear outer group is a single element.

 

The f/8 SA (this is the original SA design) has 8 elements in 4 groups. Its front outer group is a single element. Its front inner group has three cemented elements. Its rear inner group also has three cemented elements. Its rear outer group is a single element.

 

These assertions based on lens cross sections from Zeiss and Schneider.

 

Oh and by the way, both designs have been patented in the US. The USPTO thinks they're different.

 

The Wikipedia article is wrong. So much for collective wisdom. Pooled ignorance is ignorance.

 

Cheers,

 

Dan

Agreeing, nothing in wikipedia (as every information in the web or elsewhere) can be considered as a devine wisdom, they are (according to a recent research underlying the same restrictions) better in statistics then the encyclopedica britannica.

Nice try, Martin, but in this instance the wikis are wrong.

Dan, I don't think the Wikipedia article is trying to say that the Biogen and Super-Angulon are absolutely identical when it says that "The Super-Angulons are Biogon designs, making for huge, heavy lenses, but also giving very generous angles of coverage." I think that the meaning is that the Super-Angulon is the same design-type as the Biogen. Kingslake discusses the patent issues.

How does edge illumination (i.e. falloff) differ between the SA and the Biogons in general? Are there counterexamples?

Also, the next sentence in the Wikipedia article is "The f/4 lenses give 95ﾰ of coverage, the f/8 models give 100ﾰ, and the f/5.6 units give a 105ﾰ coverage angle." It is clear that the article is talking about Super-Angulons in general, and not the very first one. It can't be claiming that all Super-Angulons are exact copies of the first Biogen, but rather that Super-Angulons are of the same design-type. And Zeiss also uses the Biogen name for lenses of a design-type.

David, the point is that the Biogens and Super-Angulons use a design method to improve illumination, and have about the same off-axis illumination on the film, typically going as about cosine to the third of the angle off-axis. Both Schneider and Zeiss publish graphs of the illumination (as does Rodenstock) for their recent lenses. I have frequently cited the cosine to the fourth law here -- if you examine the Rodenstock and Schneider datasheets, you will find that it works very well for most LF lenses, so these are your counterexamples. As Pete says, the law is not immutable -- it is based on some asumptions about the lens design, and if the design deviates from those assumptions, so can the illumination. In smaller formats, retrofocus lenses won't follow the cosine to the fourth rule.

 

Here are some previous discussions: http://www.photo.net/bboard/q-and-a-fetch-msg?msg_id=005gK2 and http://www.photo.net/bboard/q-and-a-fetch-msg?msg_id=005AC8

Michael, Thanks for the answers and links. Exactly what I wanted to know. Especially the stuff about center filters in one of the links.

The 75mm lenses are among my few favorites.

 

When time permits, I will shoot side-by-side comparisons of the 75mm Super-Angulon, the 75mm Biogon and borrow a Super 76mm Biogon.

 

Nudge me if I forget.

Michael, Being picky, may I ask why you are typing, "Biogen"?

 

Also, when does a design variation becomes classified as a separate desing on its own (e.g. Anastigmat, Tessar, Topogon).

 

Pico, What is a "Super Biogon 76mm" lens? I know only the 75/4.5 Biogon (I have a sample of it as well).

But Michael, Bertele patented the Biogon design. Schneider patented the SA design. They aren't the same. They're sort of similar, but so are nearly all modern wide angle designs.

 

On the more general topic of wikipedia reliability, read a bit down the link that Pico provided and check what they say about the Symmar. They assert that the pre-WWII and modern Symmars are the same design. And here I'd always thought that the old 'uns were 6/2 double anastigmats rather similar to the better-known Goerz Dagor and the modern ones were 6/4 plasmats. But then, some people think that plasmats are just dagors in disguise.

 

And then go down to see what the wikis say about Isconars. Your hair will curl.

 

To curl your hair more, look at their remarks on G-Clarons. "The Grafik-Clarons are 6-element, 4-group, symmetrical dialyte-type lenses" Wrong wrong wrong. Early G-Clarons are 6/2 double anastigmats, newer ones are 6/4 plasmats, and there ain't no 6/4 dialytes.

 

The Wikis have collected and published misinformation about Schneider's products. The right thing to do is tell them they've been careless. You shouldn't try to find reasons why their misstatements could be construed as correct.

 

Cheers,

 

Dan

<p><i>'Michael, Being picky, may I ask why you are typing, "Biogen"?'</i> By mistake.</p>

 

<p><i>"Also, when does a design variation becomes classified as a separate desing on its own (e.g. Anastigmat, Tessar, Topogon)."</i>

It's best based in the principals of the design; also the number and configuration of the elements. The authors of books on lens designs mostly but don't entirely agree on classifying lenses since there is some judgement involved. And modern lenses for small formats are so complicated that maybe classifying some of them isn't possible.</p>

</p>

 

<p><i>"But Michael, Bertele patented the Biogon design. Schneider patented the SA design. They aren't the same. They're sort of similar, but so are nearly all modern wide angle designs."</i> Dan, I don't think anyone is trying to say that the original Biogon and any of the Super-Angulons are identical. Yes, almost all modern super-wide coverage lenses use this design technique and so belong to this design family (which many people name after the Biogon). This doesn't make this a useless classification: there are modern super-wide coverage LF lenses which don't belong to this design family, e.g., the Super-Symmar-XL. And the Super-Symmar-XL lenses have the worse cosine to the fourth illumination behavior according to Schneider's datasheets.</p>

Michael, "The Super-Angulons are Biogon designs" is a pretty strong statement. And when I cut-and-pasted I left out no qualifiers.

 

What's your take on the wikinonsense I pointed you towards?

 

Cheers,

 

Dan

The old Angulons (no super) are also 6/2 "biogons" (wiki speak).

 

Wiki and goggle and.. thank heavens!

Wikipedia doesn't yet have an article defining Biogon.

 

I assume that Vivek is joking. All the books make the point that the Biogon-type has LARGE negative outer elements. If you compare a 90 mm Angulon with a 90 mm Super-Angulon, you will instantly notice that the plain Angulon is much smaller. If you look at cross-section diagrams, the elements on the Angulon are cemented into two groups, one on each side of the aperture, as noted by Vivek, while the large, negative outer elements of a Biogon-type are airspaced from the center, no doubt to give space for the rays to bend towards the elements of the positive core.

Dan, the Wikipedia article has the errors you point out, such as the design of the G-Claron. I noticed others, such as implying that all Symmar-S lenses are multicoated (cf. http://www.schneideroptics.com/info/faq/photography.htm#q8). But I think that the design description of the Super-Angulon is correct, but imperfectly worded. The right thing to do is to edit the article.

Michael, Of course, it was a joke. The nicest historical story (accurate) of Biogon design that one can find on the net without having to read through a few authoritative books is from you (the link you gave above).

There are errors even in the optical textbooks, trade catalogs too. It is wise to no always believe what one reads. Marketing chaps sometimes tranpose numbers, transpose columns of data. Sometimes the same optical diagram is cut and pasted to a new lens design's specs. In the Graphics Arts Insdustry, many versions of the Schneider Componon were available in shutter. Folks on P.net will ask if it is possible to a Componon in shutter, a few afolks will respond no, and there was one on Ebay in shutter while the thread is active! A common error is that some sites say all Ektars are 4 elements, 3 groups, ie a Tessar. Many Ektars are, some are not. There are 3,4,5,6 etc element ektars. A review of the patent literature andf some doubting thomas attiude is wise when doing researching. The camera makers sites often omit lenses that were made too.

Some lenses that are based on other older lenses look nothing like their predecessors,

because by splitting, merging, and grouping you create very different looking block

diagrams.