Double Gauss Designs

woodrim · Joined: 14 Jan 2010 Posts: 4060 Location: Charleston

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.

Lloydy · Expire: 2022-01-01

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

fermy · Joined: 17 Feb 2012 Posts: 1974

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.

Lightshow · Joined: 04 Nov 2011 Posts: 3666 Location: Calgary

Thanks for the diagrams. Smile

patrickh · Expire: 2011-11-18

Fascinating

patrickh

RAART · Posted: Thu Dec 27, 2012 4:49 am Post subject:

Captivating!
Idea

tromboads · Expire: 2015-10-01

.. Hears the pokemon theme song.. Got a catch em all, double gause!

Excalibur · Expire: 2014-04-21

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

casualcollector · Posted: Thu Dec 27, 2012 1:04 pm Post subject:

Mos6502 · Joined: 20 Jun 2011 Posts: 960 Location: Austin

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

Keysersoze27 · Expire: 2012-12-24

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...

woodrim · Joined: 14 Jan 2010 Posts: 4060 Location: Charleston

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?

Excalibur · Expire: 2014-04-21

tromboads · Expire: 2015-10-01

A Tessar.... Your eyes are doing better then mine, we need 3 systems, er groups, and fourish elements?

skida · Posted: Fri Dec 28, 2012 2:23 am Post subject:

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!

Mos6502 · Joined: 20 Jun 2011 Posts: 960 Location: Austin

fermy · Joined: 17 Feb 2012 Posts: 1974

Ufff, found it, but had to go through the list a couple of times. Pentax lens.

56 DIN · Expire: 2021-11-18

thanks a lot

JohnBar · Joined: 21 Jun 2012 Posts: 581 Location: Liverpool

Schneider have produced a number of DG variations which do not appear in those charts, Xenon, Xenar etc

MacTak · Joined: 15 Jun 2011 Posts: 108

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.

Ray Parkhurst · Posted: Tue Jan 07, 2014 3:06 pm Post subject:

danfromm · Joined: 04 Sep 2011 Posts: 595

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.

danfromm · Joined: 04 Sep 2011 Posts: 595

sichko · Joined: 20 Jun 2008 Posts: 2475 Location: South West UK

spoilerhead · Joined: 25 Jan 2012 Posts: 68 Location: Austria