classic optical formula

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zozio32

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I am interested in learning a bit more about the classic optical formula, what they their photographic specificity, and which one are still in use.

So far, I think we have only the Zeiss sonnar and some CV heliar that are using classic formula with maybe minor changes (the new 75mm 1.9 classic heliar as 6 elements instead of 5 in the new one).

Basically, I like the "old" look, but I want modern coatings ;) -> I like the look from my J8, but contrast and flare resistance are not up to my pentax smc lenses

So, can you make a difference between the signature of the different formula, and did I miss some of them?
 
Buy Photographic Optics by Arthur Cox, which is a wonderful historical survey with a lot of diagrams at the back showing how designs are related.

Do not assume, however, that such lenses as today's 1,5/50 C-Sonnar is quite as 'classic' as you seem to think -- going to 4 groups instead of 3 is not what I would call a minor change.

Cheers,

R.
 
Well, it's pretty close as it looks like. Is not only about using an air element instead of glass element cemented between the 2nd and 4th of the 1932 design?

anyway, I'll check the reference you're mentioning. Thanks
 
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pretty sure that the ZM Sonnar is a planar design, and is not directly related the old Sonnar design like the classic Contax lens or the J-3
 
zozio32 said:
Well, it's pretty close as it looks like. Is not only about using an air element instead of glass element cemented between the 2nd and 4th of the 1932 design?
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Well, yes, but a Tessar is 'only' a Cooke Triplet with the back singlet replaced by a cemented doublet. Replace the front glass with a cemented doublet as well, and you have the Heliar, Color Heliar and Apo Lanthar. And so forth.

EDIT: Cox also shows four different sections for Planars of different focal lengths. The most usual design (6-glass 4-group symmetrical, 1-2-2-1) is also used for the Biotars from 24 to 58mm, but the 55/1.4 Planar splits the rear glass into two singlets and the Planar for 6x6 uses a singlet instead of a cemented doublet for the second group.

SECOND EDIT: The C-Sonnar is a 6-glass, 4-group lens, with the second group consisting of an air-spaced pair of glasses instead of a cemented triplet, but still recognizably a Sonnar.

Cheers,

R.
 
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sevo said:
Maybe. Zeiss claims in http://www.zeiss.com/C12567A8003B8B6F/EmbedTitelIntern/CLN_39_en_Tessar/$File/CLN39_en_tessar.pdf that the Tessar is a hybrid of a Unar front with Anastigmat back group (both being recent Zeiss developments at the time) rather than derived from the Triplet.
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Absolutely. That's why 'only' is in quotation marks. The evolution of lens design often involves company pride as well as questions of opinion. Thus, one might cheerfully call a 5cm Elmar a Tessar-type, except that (as far as I recall) Leica reckons it is a simplification of the 5-glass Anastigmat.

All this talk of lens history, 'classic' designs, etc., is put in perspective by a comment from Dr. Nasse at Zeiss: "You never really know how a lens is going to behave until you build it." In other words, once you vary the curvatures or glass types, let alone the number of glasses and groups, you've got a different lens, and the name is as much a marketing or nostalgic decision as a matter of design.

Cheers,

R.
 
The 50mm ZM Sonnar is absolutely a Sonnar. As zozio32 points out, the primary difference between the ZM design and the old design is the removal of the middle glass element from the front triplet, leaving an air gap. The glass-air-glass is still a triplet, with the air gap functioning as an air lens.


Cheers,

David
 
dberger said:
The 50mm ZM Sonnar is absolutely a Sonnar. As zozio32 points out, the primary difference between the ZM design and the old design is the removal of the middle glass element from the front triplet, leaving an air gap. The glass-air-glass is still a triplet, with the air gap functioning as an air lens.


Cheers,

David
Click to expand...
Dear David,

As well as the current 6-glass 3-group C-Sonnar, the Sonnar name has been used on a 4-glass, 4-group lens (250/5.6 for 35mm); a 4-glass, 3-group (135/4); a 5-glass 3-group (150/4, 180/4.8, 250/5.6 for rollfilm); a 6-glass, 3-group (50/2); and a 7-glass, 3-group (50/1.5, 85/2). Arguing about what is 'absolutely a Sonnar' is therefore well open to interpretation.

Cheers,

R.
 
I guess we can maybe talk of family of optical formula. If I read correctly, there was only 6 element in the original sonnar 5cm f2. As long as they have similar type of optical characteristics, I am happy.

I guess a good start would be to make the difference between symmetric design like the Heliar or Planar and the design like the Sonnar. Any fundamental different optical properties there?

Well, i guess I should get a text book of lens design...
 
For exemple, is their an "heir" to the schneider xenotar of the rolleiflex 3.5F with modern coatings?

I'll be quite interested to find one, either for a rangefinder or a SLR. I really like how the lens render the transition between focus and blur. I know it's a bit due to the format but well, I am sure the lens design plays a part in that.
For the look of the diagram, it's also a non symmetric design, not that far away from a Sonnar actually
 
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zozio32 said:
For exemple, is their an "heir" to the schneider xenotar of the rolleiflex 3.5F with modern coatings?
Click to expand...

The Schneider Xenotar on the Rolleiflex is essentially a six element Planar design - there are many of those knocking around for pretty much every camera system. If you use a Pentax SLR (you mentioned you used SMC lenses) then any of the 50/1.4's from the Super-Takumar right up to the FA50 should give a broadly similar performance.
 
The question is what makes an optical formula? Most people count elements and groups, whether an element is positive or negative.
Equally important (maybe even more) are parameters like radius, space between elements and glass type. Coating is a major factor when it comes to contrast. These are typically omitted when talking about "lens formula".
You can design a planar type lens with pleasing soft or harsh OOF rendering and you will see no difference when viewing a lens cross section.
 
that's interesting ath.
I'll thought that with the choice of a formula, you'll had gone a long way into defining the character of the lens.
 
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