CZJ Tessar 2.8/5cm: Pre-war vs post-war computation

stevemark · Joined: 29 Apr 2011 Posts: 3754 Location: Switzerland

Paul Rudolph's Tessar is - along with his earlier Planar - certainly one of the most important lens constructions ever. It's patent, an f5.5 Tessar, was issued in 1902. The first production Tessars were f6.3 Tessars for large format photography.

Not much later Rudolph's assistant Wandersleb re-fined the original computation to f4.5 (1905) and even to f3.5 (1906). The latter was re-compute in 1926, using newer glasses to improve its performance.

In 1930 Williy Merté published its f2.8 Tessar. That was pretty much the limit of the Tessar design. It seems that Zeiss was not happy with the first small production run of the f2.8, and subsequently the calculation was slightly improved. Even that wasn't satisfying: After only 10'000 units produced, Merté tried again to impove it. This third sub-variant was produced until at least 1945, and probably after the war as well.

Interestingly, there was only one major re-calculation of Mertés Carl Zeiss Jena Tessar 2.8/50mm after the WWII: It was recalculated / improved in 1951 by Zöllner. The same design then was produced without major optical changes until about 1990.

More on the Tessar history e. g. on Zeissikonveb.de (a superb site, BTW)

I have compared these two calculations -

1) a prewar Merté (1937) Carl Zeiss Jena Tessar 1:2.8 f=5cm (uncoated, Nr.2044640)
2) a postwar Zöllner (around 1954) Carl Zeiss Jena Tessar T 1:2.8 f=50mm (coated, Nr.3811457)
3) a postwar (around 1973) Carl Zeiss Jena DDR Tessar 2.8/50 (coated, Nr.9781274)

All three lenses look pertty nice: No dents, no abvious signs of damage, and no scratches on the glass. Both the 1937 as well as the 1954 lens have slight fogging; the 1973 is pretty clean. The aperture of the 1973 version however does not close beyond f4.5.

Let's start with the center, and 100% crops from the 43 MF JPGs of the Sony A7RII. This camera of course is extremely demanding for a >90 years old lens ...

Both Tessar f2.8 computations have a pretty high resolution, but the prewar uncoated Tessar lacks constrast, of course. In addition - not visible hear - it suffers from a strong focus shift of the image when stopping down. When stopping down from f2.8 to f4 I had to re-focus; otherwise the center crop simply would have been unsharp! For comparison: the Minolta MD 2/50mm at the bottom.

iangreenhalgh1 · Expire: 2014-01-07

it would be far more instructive to compare the Jena Tessar that continued almost unchanged for so long to the Western compatriots that did changhe over time due to new technology - better coating, better glass types, digital computers to do the optical formulations.

The Schneider Xenar is pretty much identical to the Tessar but was recalculated postwar, same with the Voigtlander Color-Skopar, which is usually better than a Jena Tessar equivalent, becausew it had the benefits of Lanthanum glass and having been recaluclated in the 50s by a digital computer - the Color-Skopar is a significant improvement on the Skopar and many rated it as the best Tessar variant.

Then there is the Zeiss Tessar itself, the western version is outwardly the same as the DDR version.

Then there is whole other can of worms of the Russian Industar series, which began as direct copies of Jena tessars but evolved to use different glass types available in Russia.

stevemark · Joined: 29 Apr 2011 Posts: 3754 Location: Switzerland

PLEASE CLICK TWICE ON THE IMAGES TO GET THE FULL RESOLUTION (=100% COPS) !!

Very close to the center - just a few mm away - the resolution of fine structures starts to drop:

At the border things look like that (about 17mm from the center):

And finally at the corners (about 21mm from the center):

Up to now I hadn't been aware of the differences between these two main calculations of the CZJ f2.8 Tessars.
And it's pretty interesting to see the differences between "uncoated" and "coated", too.

S

D1N0 · Joined: 07 Aug 2012 Posts: 2491

Tessars should really start at 3.5 not 2.8. The 70's ones have horrible build quality, so probably a lot of copy variation. Still you can take good images with them

stevemark · Joined: 29 Apr 2011 Posts: 3754 Location: Switzerland

iangreenhalgh1 · Expire: 2014-01-07

You're talking about the East German ones, which were dodgy in build quality after the 60s chrome ones.

But in the West, they were making very fine quality Tessar 2.8/50s, just mostly they went onto fixed lens cameras. The Tessar 2.8/50 for the Contaflex is a superb optic, I mounted mine for use on my NEX years ago, it's noticably better than an Eastern compatriot.

If you really want to see how good the 2.8/50 tessar type can be, you need a Color-Skopar or a Xenar.

An interesting test would be the Color-Skopar and Xenar from the respective DKL mount series of Voigtlander and Schneider for the Kodak Retinas alongside a western Tessar 2.8/50 and an Eastern Tessar 2.8/50. Then throw in a couple of Russians such as the Industar-50 and the Industar-61L/D.

If not restricted to the 50mm legth, Ross made some Xpres tessar types that rival anything else in that formula from any manufacturer.

stevemark · Joined: 29 Apr 2011 Posts: 3754 Location: Switzerland

cbass · Joined: 27 Jul 2019 Posts: 441

Interesting evolution.
Looks like the eagle eye has aged.

D1N0 · Joined: 07 Aug 2012 Posts: 2491

papasito · Joined: 09 Jan 2015 Posts: 1658

iangreenhalgh1 · Expire: 2014-01-07

Yes, that Tessar is a Color-Skopar, they simply used the Zeiss name as it was released after the ZI-Voigtlander merger. The Icarex lenses are simply Voigtlanders under Zeiss names.

stevemark · Joined: 29 Apr 2011 Posts: 3754 Location: Switzerland

iangreenhalgh1 · Expire: 2014-01-07

Use some common sense, for that Xenar to perform that badly means it's a bad copy.

Do you honestly think Schneider were still using a pre-war computation as late as 1957?

The glass types had changed for one thing, by 1957 Schott and other glassmakers were making widespread use of Lanthanum, which meant lenses had to be recalculated - one example is Voigtlander recalculating the Skopar to use Lanthanum glass and thus creating the Color-Skopar. Tronnier lead the project and they patented the new calculation in the US in 1949:

A postwar Schneider catalogue states that the Xenar has been updated to use the new glass types:

So no, the postwar Xenar is not the pre-war Tessar with coating added.

stevemark · Joined: 29 Apr 2011 Posts: 3754 Location: Switzerland

iangreenhalgh1 · Expire: 2014-01-07

Well, there must be something wrong with the lens or the test because the Xenar is never that bad.