Docter Optic Tessar, Apo-Germinar MTF curves

[Dan Fromm]

Ridax, read the paper carefully. It makes the point that the Russars evaluated were far off specifications and were, in particular, badly centered. I'm surprised that imperfect mapping lenses were let out of the factory. The application requires a quality lens.

The Orion Ias I mentioned were offered as aerial camera lenses and their mountings were consistent with this. The most commonly reported problem was poor front elements with steps. Aspherical, probably unintentionally.

Ian made the point that he and friends have had hundreds of FSU lenses, mainly for 35 mm cameras, between them and that very few of these lenses were "duds." There's no disputing tastes, but Ian and friends say wonderful things about other lenses for, mainly, 35 mm cameras for which no tests were published by the US magazines Modern Photography and Popular Photography. There are many reasons why neither magazine published tests of every lens on the market; one was that the example of the lens tested wasn't very good. It is impossible to tell whether neither magazine reported on a lens because of lack of space or time (so many lenses, so little time and so few pages for tests) or because the lens was poor. The two magazines tested at distance at every marked f/stop, reported measured resolution and contrast center and edge, expected better performance from lenses around normal focal length than from wide angle or long lenses; in addition they published and discussed pictures, not just USAF 1951 targets, taken with the tested lens.

Re lens tests not published in MP or PP, I once asked the late Norman Rothschild, who wrote for PP, why PP had never published a test of any 55/3.5 MicroNikkor. He said that all of the 55/3.5 MicroNikkors tested produced unacceptable results at some apertures at distance. I've had one, shot it happily at all distances. I never brought that up with Mr. Rotschild, but I know his answer. Unsystematic "tests" aren't always very informative. To bring the discussion back to LF, this is true of LF lenses too. In the end, what matters most is whether the images produced please, not whether the lens used tests well.

Cheers,

Dan

[Ian Greenhalgh]

I don't put much stock in tests. I can safely say that the Russian Zeiss copies for 35mm compare very well to the Zeiss originals, if both are in good condition.

[ridax]

Ridax, read the paper carefully. It makes the point that the Russars evaluated were far off specifications and were, in particular, badly centered. I'm surprised that imperfect mapping lenses were let out of the factory. The application requires a quality lens.

Well, I've just reread every word of it. Sorry Dan but the above statement of yours is not correct. First, the authors never head the opportunity to see the actual factory standards for the lenses (and those specs are never mentioned in the paper in fact) so they were unable to judge if the lenses were to be manufactured better but were screwed up in production, or those lenses actually were intended to be made as loose as they came out. I believe the majority of the discussion participants were inclined to the latter point of view, i.e. no QC problem with those Russars; they were manufactured like this on purpose (with the purpose apparently being the cost efficiency). More so, the discussion reveals several means to make good maps with that imperfect lenses, and the common belief is, one or another of those means was actually in use in Russia. That sounds true enough - keeping in mind the talk is about the world-first lenses of the type, with really hard to manufacture large deeply curved elements, designed in 1945 and manufactured in the days when half of the industrial Russia was in ruins, and it probably was more reasonable to develop and apply that external correction means rather then put more effort into the lenses' production. And there was also no wonder the 1945 lens looked inferior to the glasses the high-end pros were accustomed to in 1973.

And anyway, the issues pointed in the paper are totally irrelevant for general photography. Those guys are talking microns of distortion!

I really can't comment much on the particular Orions that I've never seen myself but reports on poor front elements with no similar reports on rear elements seem suspicious. Aren't the front and the back of the topogons exactly the same? If the fronts are bad why the backs aren't? Those fronts may well have got scratched badly and later repolished by some dude's evil hand just before the poor glasses were put for resale. Personally, I have seen things like that happen on the secondary market.

And yes resolving power numbers make more sense when there are lots of them, not just the two center-and-corner ones. But even then the field curvature question still remains - as well as a number of other questions that one is unable to answer until he/she actually tries the lens in the field... Not that I thought it was a fresh idea :) but I've seen a lot of beginners too mesmerized by those published numbers, and the point I'd want to make is just this: don't think about numbers and graphs for too long, get to taking pictures instead. For, as you said, what matters most is whether the images produced please.

[ridax]

I can safely say that the Russian Zeiss copies for 35mm compare very well to the Zeiss originals, if both are in good condition.

Yes I'd say just the same - except for the coating. That was always the major PITA with the Russian lenses. Yes some of them happen to have the coating as good as the German one but most do not. And then some are less prone to flare due to the elements curvature and position; those do not suffer from the inferior coating too much. But others do. Though again the difference may often be not too important depending on the application....