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Double Gauss Designs
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PostPosted: Thu Dec 27, 2012 1:15 am    Post subject: Double Gauss Designs Reply with quote
I have posted this as a separate thread to make it easier to find in any future searches. Here are three charts of double gauss designs. You will need to click on the images to get one at a size that you can read.







PostPosted: Thu Dec 27, 2012 1:26 am    Post subject: Reply with quote
What we need now is a simple explanation of this type of lens design so that the simple folk, like me, can understand the basics of the design and the benefits, downfalls etc. I guess I'm not alone in hearing and reading about the different designs and not fully understanding and appreciating the differences, and more importantly the difference it makes when I press the button.
But remember ------ 'simple' Wink


PostPosted: Thu Dec 27, 2012 2:29 am    Post subject: Reply with quote
In simple terms it's the best design for a normal lens that can be hand calculated. The basic concept is clearly seen in the first lens here (Kodak Ektar): two convex lenses separated by air followed by their mirror image. The design is symmetric. The key advantage of design is that it allows good correction of various aberrations, allowing for very fast lenses. The disadvantage is that double-Gauss have a lot of glass-air surfaces, so require coating.

The designs that were popular before double Gauss: Tessar and Sonnar have fewer glass-air surfaces and can function uncoated. However, they have more aberrations, will be noticably weaker away from the center than double Gauss, but will have better contrast given the same coating. In practice, one might prefer Sonnars for portrait lenses as uncorrected spherical aberrations will result in smoother rendering.


PostPosted: Thu Dec 27, 2012 3:36 am    Post subject: Reply with quote
Thanks for the diagrams.Smile


PostPosted: Thu Dec 27, 2012 4:25 am    Post subject: Reply with quote
Fascinating


patrickh


PostPosted: Thu Dec 27, 2012 4:49 am    Post subject: Reply with quote
Captivating!
Idea


PostPosted: Thu Dec 27, 2012 8:32 am    Post subject: Reply with quote
.. Hears the pokemon theme song.. Got a catch em all, double gause!


PostPosted: Thu Dec 27, 2012 9:16 am    Post subject: Reply with quote
Very interesting but doesn't explain why some lenses are sharper\better than others (ignoring misuse or bad copy or type of glass)..e.g why is the Minolta PG 50mm f1.4 sharper than the Minolta PF 58mm f1.4 and similar comparisons. Or why everyone praises the RE Topcor 58mm f1.4 but ignores the Minolta PF 58mm f1.4 manufactured roughly at the same time......is the answer simply:- Minolta are inferior compared to Topcon in turning out lenses, so pick your own examples and wonder why Question


PostPosted: Thu Dec 27, 2012 1:04 pm    Post subject: Reply with quote
Excalibur wrote:
Very interesting but doesn't explain why some lenses are sharper\better than others


Different goals on the designer's part. Different capabilities of the manufacturer. Economic considerations (selling price). Different quality standards of makers. Sample variation. Differing tastes of user.

I have an issue of Camera 35 Magazine from 1971. The Canon F-1, Pentax Spotmatic F and Mamiya/Sekor Auto XTL were tested with their f-1.4 standard lenses. I believe this was a test chart on film test. The Canon had the best numbers with Pentax and Mamiya falling in behind. Today it seems the Pentax Super Takumar is the most highly praised and desirable of the group, judged by the comments of this forum.


PostPosted: Thu Dec 27, 2012 1:51 pm    Post subject: Reply with quote
One lens up there is a tessar variant, not a double guass, can you spot it? Smile

casualcollector wrote:
Excalibur wrote:
Very interesting but doesn't explain why some lenses are sharper\better than others


Different goals on the designer's part. Different capabilities of the manufacturer. Economic considerations (selling price). Different quality standards of makers. Sample variation. Differing tastes of user.

I have an issue of Camera 35 Magazine from 1971. The Canon F-1, Pentax Spotmatic F and Mamiya/Sekor Auto XTL were tested with their f-1.4 standard lenses. I believe this was a test chart on film test. The Canon had the best numbers with Pentax and Mamiya falling in behind. Today it seems the Pentax Super Takumar is the most highly praised and desirable of the group, judged by the comments of this forum.


One thing is that designers had to work around each other presumably, some designers were just better than others, or had other goals (ie. speed vs. sharpness, or aberrations vs. distortion etc.) so lenses of similar design perform differently, and as pointed out constraints of selling price, materials, etc. also make differences.

Lenses which are in "convenient" mounts like M42 will be more popular these days than lenses in esoteric mounts, which pretty much explains why the Takumars are more popular than other lenses which are as good or better but only available in other mounts.


PostPosted: Thu Dec 27, 2012 2:03 pm    Post subject: Reply with quote
Woodrim very nice work !!!!!

You could also add the Fujinon 55 f1.8 and use the Zuiko Auto-S 50mm f1.8 diagram since it is the same at 98% Wink

Also the Yashica line of 50mm lenses is also in the same category...


PostPosted: Thu Dec 27, 2012 2:27 pm    Post subject: Reply with quote
To me, the most interesting thing was to find the Vivitar 90/2.5 Series 1 Macro there; one of my favorite and treasured lenses. Who were Opcon?


PostPosted: Thu Dec 27, 2012 3:05 pm    Post subject: Reply with quote
casualcollector wrote:
Today it seems the Pentax Super Takumar is the most highly praised and desirable of the group, judged by the comments of this forum.


...........or until recently (e.g Nex) most Digital users couldn't use old Canon FD lenses (well they could but it was inconvenient and with some problems) so less comments made Question


PostPosted: Thu Dec 27, 2012 10:30 pm    Post subject: Reply with quote
A Tessar.... Your eyes are doing better then mine, we need 3 systems, er groups, and fourish elements?



Mos6502 wrote:
One lens up there is a tessar variant, not a double guass, can you spot it? Smile

casualcollector wrote:
Excalibur wrote:
Very interesting but doesn't explain why some lenses are sharper\better than others


Different goals on the designer's part. Different capabilities of the manufacturer. Economic considerations (selling price). Different quality standards of makers. Sample variation. Differing tastes of user.

I have an issue of Camera 35 Magazine from 1971. The Canon F-1, Pentax Spotmatic F and Mamiya/Sekor Auto XTL were tested with their f-1.4 standard lenses. I believe this was a test chart on film test. The Canon had the best numbers with Pentax and Mamiya falling in behind. Today it seems the Pentax Super Takumar is the most highly praised and desirable of the group, judged by the comments of this forum.


One thing is that designers had to work around each other presumably, some designers were just better than others, or had other goals (ie. speed vs. sharpness, or aberrations vs. distortion etc.) so lenses of similar design perform differently, and as pointed out constraints of selling price, materials, etc. also make differences.

Lenses which are in "convenient" mounts like M42 will be more popular these days than lenses in esoteric mounts, which pretty much explains why the Takumars are more popular than other lenses which are as good or better but only available in other mounts.


PostPosted: Fri Dec 28, 2012 2:23 am    Post subject: Reply with quote
I have to admit doing a search on "Double-Gauss" Embarassed

Clever bloke, that Carl Friedrich Gauss: when he wasn't playing with magnets he was designing telescope lenses!


PostPosted: Fri Dec 28, 2012 3:05 am    Post subject: Reply with quote
tromboads wrote:
A Tessar.... Your eyes are doing better then mine, we need 3 systems, er groups, and fourish elements?



Mos6502 wrote:
One lens up there is a tessar variant, not a double guass, can you spot it? Smile

casualcollector wrote:
Excalibur wrote:
Very interesting but doesn't explain why some lenses are sharper\better than others


Different goals on the designer's part. Different capabilities of the manufacturer. Economic considerations (selling price). Different quality standards of makers. Sample variation. Differing tastes of user.

I have an issue of Camera 35 Magazine from 1971. The Canon F-1, Pentax Spotmatic F and Mamiya/Sekor Auto XTL were tested with their f-1.4 standard lenses. I believe this was a test chart on film test. The Canon had the best numbers with Pentax and Mamiya falling in behind. Today it seems the Pentax Super Takumar is the most highly praised and desirable of the group, judged by the comments of this forum.


One thing is that designers had to work around each other presumably, some designers were just better than others, or had other goals (ie. speed vs. sharpness, or aberrations vs. distortion etc.) so lenses of similar design perform differently, and as pointed out constraints of selling price, materials, etc. also make differences.

Lenses which are in "convenient" mounts like M42 will be more popular these days than lenses in esoteric mounts, which pretty much explains why the Takumars are more popular than other lenses which are as good or better but only available in other mounts.


In this case it has five elements. The maximum aperture is another give away.


PostPosted: Fri Dec 28, 2012 3:59 am    Post subject: Reply with quote
Ufff, found it, but had to go through the list a couple of times. Pentax lens.


PostPosted: Fri Dec 28, 2012 1:11 pm    Post subject: Reply with quote
thanks a lot


PostPosted: Fri Dec 28, 2012 2:34 pm    Post subject: Reply with quote
Schneider have produced a number of DG variations which do not appear in those charts, Xenon, Xenar etc


PostPosted: Tue Jan 07, 2014 12:04 pm    Post subject: Reply with quote
Forgive me for dredging up an old thread, but I thought this would be the perfect thread to make some mention (and hopefully get a little discussion) of the new Sigma 50mm f1.4 Art lens announced today. For it features a very strange and (I think) novel design: the first quadruple-Gauss lens!?



Let's start with the rear half of the lens, which would itself be a relatively expected design for a fast 50--a Biotar/Xenon type, though one with a particularly enhanced rear group (two elements in the rear has been done on some fast 50mm, but here one of those elements is turned into a doublet and the other is aspherical). This rear half is much the same as the entire prior Sigma 50mm f1.4 DG EX lens (including that enhanced rear group with doublet + aspherical), except that lens split the front doublet (Ultron-type). But then there is also the whole front part of the lens design, and guess what, it clearly looks like another double-Gauss feature (stripped of any extra elements besides the opposed Gaussian elements themselves). In this case the front group remains split, and the rear group, instead of being the usual doublet (or split), has been made into a triplet! Like I said, pretty crazy.


PostPosted: Tue Jan 07, 2014 3:06 pm    Post subject: Reply with quote
woodrim wrote:
To me, the most interesting thing was to find the Vivitar 90/2.5 Series 1 Macro there; one of my favorite and treasured lenses. Who were Opcon?


Have you seen the M42 mount Vivitar 90/2.5 on eBay? It has 25 watchers. The 1:1 converter is in a separate auction. Serial number starts with 378, so am I correct to assume this is the Opcon version?


PostPosted: Tue Jan 07, 2014 3:12 pm    Post subject: Reply with quote
Interesting thread that I missed when it was young. I'm glad it was resurrected and made visible again.

Doubly interesting because it is so sharply focused on fast narrow angle (normal) lenses for, mainly, 35 mm still. It omits 4/4 double Gauss wide angle types used on larger formats, e.g., Kodak Wide Field Ektar; Cooke Ser. VIIb and other similar lenses from Dallmeyer, Ross and Wray; Meyer Aristostigmat; CZJ's Topogon and all of the Topogon derivatives from many makers. It also omits slow narrow angle process lenses such as Lomo's f/10 RF-2, ..., RF-5.

Surprising in that it missed TTH's 6/4 double Gauss types completely.

The Sigma thingy is strange. No way are the first three groups a double Gauss type, the third group is a more or less a single Dagor (or clone) cell. The rearmost group is a little hard to read, not clear whether it contains a cemented doublet, air space, and cemented triplet (Dagor-like, again) or is five elements cemented together. Either way, not half of a conventional fast double Gauss type. Calling the lens a quadruple Gauss type is a large stretch.

Interesting phenomenon, trying to stretch an old idea to include what seems to be a new one.

Last edited by danfromm on Tue Jan 07, 2014 3:17 pm; edited 1 time in total


PostPosted: Tue Jan 07, 2014 3:14 pm    Post subject: Reply with quote
JohnBar wrote:
Schneider have produced a number of DG variations which do not appear in those charts, Xenon, Xenar etc


The Xenon started out as a 6/4 f/2 double Gauss type licensed from TTH, turned into a trade name that includes other design types, all fast.

The Xenar is Schneider's Tessar.


PostPosted: Tue Jan 07, 2014 3:35 pm    Post subject: Reply with quote
MacTak wrote:
Forgive me for dredging up an old thread, but I thought this would be the perfect thread to make some mention (and hopefully get a little discussion) of the new Sigma 50mm f1.4 Art lens announced today. For it features a very strange and (I think) novel design: the first quadruple-Gauss lens!?



Let's start with the rear half of the lens, which would itself be a relatively expected design for a fast 50--a Biotar/Xenon type, though one with a particularly enhanced rear group (two elements in the rear has been done on some fast 50mm, but here one of those elements is turned into a doublet and the other is aspherical). This rear half is much the same as the entire prior Sigma 50mm f1.4 DG EX lens (including that enhanced rear group with doublet + aspherical), except that lens split the front doublet (Ultron-type). But then there is also the whole front part of the lens design, and guess what, it clearly looks like another double-Gauss feature (stripped of any extra elements besides the opposed Gaussian elements themselves). In this case the front group remains split, and the rear group, instead of being the usual doublet (or split), has been made into a triplet! Like I said, pretty crazy.


There's a strong negative element in the front half, and the back half is positive and Double-Gauss-like. A retrofocus lens ?


PostPosted: Tue Jan 07, 2014 3:37 pm    Post subject: Reply with quote
MacTak wrote:
Forgive me for dredging up an old thread, but I thought this would be the perfect thread to make some mention (and hopefully get a little discussion) of the new Sigma 50mm f1.4 Art lens announced today. For it features a very strange and (I think) novel design: the first quadruple-Gauss lens!?



Let's start with the rear half of the lens, which would itself be a relatively expected design for a fast 50--a Biotar/Xenon type, though one with a particularly enhanced rear group (two elements in the rear has been done on some fast 50mm, but here one of those elements is turned into a doublet and the other is aspherical). This rear half is much the same as the entire prior Sigma 50mm f1.4 DG EX lens (including that enhanced rear group with doublet + aspherical), except that lens split the front doublet (Ultron-type). But then there is also the whole front part of the lens design, and guess what, it clearly looks like another double-Gauss feature (stripped of any extra elements besides the opposed Gaussian elements themselves). In this case the front group remains split, and the rear group, instead of being the usual doublet (or split), has been made into a triplet! Like I said, pretty crazy.


It looks a lot like a very sofisticated medium format wide angle design. i.e. a read block "normal lens" and a front block "wide angle converter"

compare to:
Zeiss Biogon 21mm ZM


and the medium format wideangles at http://www.marcocavina.com/articoli_fotografici/Rolleiflex_vs_Hasselblad_2/00_pag.htm

the new Zeiss Otus 55 1.4 is also similar:
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