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Thread: f/4.5 Tessars

  1. #11

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    Re: f/4.5 Tessars

    Jody, several lens makers replaced the real Tessar's cemented doublet with a cemented triplet to get around Zeiss' patent. Ross, for example with the Xpres. But Xpres is really a trade name and later Xpres lenses were really tessar types.

    Flor is an SOM Berthiot trade name, not a design type. I have in front of me some SOM Berthiot propaganda that shows cross sections. Flor includes tessar types, the cheating tessar type you described, 6/4 double Gauss types and 7/4 types derived from double Gauss.

  2. #12
    (Shrek)
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    Re: f/4.5 Tessars

    Quote Originally Posted by Dan Fromm View Post
    Jody, several lens makers replaced the real Tessar's cemented doublet with a cemented triplet to get around Zeiss' patent. Ross, for example with the Xpres. But Xpres is really a trade name and later Xpres lenses were really tessar types.

    Flor is an SOM Berthiot trade name, not a design type. I have in front of me some SOM Berthiot propaganda that shows cross sections. Flor includes tessar types, the cheating tessar type you described, 6/4 double Gauss types and 7/4 types derived from double Gauss.
    This particular Flor was post-war, almost immediately post-war in fact as the Bloc-Metal's claim to fame was the aluminum/white metal body finished to look like leather, when leather was in short supply because of the war (plus, the lens' inner surfaces are coated, and rather soft like 100/3.5 Ektar on the Medalist). I gather the Zeiss patents had been declared null & void by then, and the Bloc-Metal was part of France's effort to seize a share of the post-war camera business given the vacuum left by the destruction of most German facilities. It is in fact a fine effort, as I said this is one of my favorite lenses; the 6x9 negs might not be the sharpest ever, but they have a beautiful tonality very much like my uncoated Dagors in fact. I assume the choice to use a triplet rear was just that, a choice, as they could by then have copied the Tessar exactly.

    I have another as yet untested one on a Super Kinax III (?- not sure which version), which appears identical to the Flor but is labeled something else for some reason; everyone assumes it's the same lens.

  3. #13
    IanG's Avatar
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    Re: f/4.5 Tessars

    Quote Originally Posted by Dan Fromm View Post
    Jody, several lens makers replaced the real Tessar's cemented doublet with a cemented triplet to get around Zeiss' patent. Ross, for example with the Xpres. But Xpres is really a trade name and later Xpres lenses were really tessar types.
    It was a better lens Dan, after the outbreak of WWI the scenario changed and Ross no longer paid Zeiss any Royalties for the patents. I've an Air Ministry 141mm EWA f18 Ross lens that'sn clearly the same as the Ross Zeiss f16 Protar.

    Reality is some Xenars are 5 element yet they all classed as Tessars, many Xpres lenses are 5 element and some are Tessars, as Ross had taken over Zeiss in the UK (Mill MillHill) during WW1 , there were no issues with getting around Patents, Germany was in ruins.

    Ian

  4. #14

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    Re: f/4.5 Tessars

    I own a Rodenstock Ysar 1:4.5 15cm. It's my first Tessar, so I can't compare its performance and/or mood with others, but I'm happy with it.

  5. #15

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    Re: f/4.5 Tessars

    Jody wrote:

    This particular Flor was post-war, almost immediately post-war in fact
    Then its older than the SOM Berthiot propaganda I mentioned. Berthiot offered all of the Flor types I described at the same time, i.e., around 1950.

    Ian, what do Protars have to do with Tessars?

    Why do you say that the Xpres, any version, is better than the Tessar, any version? I ask because I have a Selfix 820 with the renowned 105/3.8 Xpres. I've never got a satisfactorily sharp shot with the wretched thing. I've checked, the lens is properly collimated. And I've checked, the lens' rear group is a doublet, not a triplet, so it is an echt tessar type. I've got satisfactorily sharp shots with the humble 101/4.5 Ektar (uncoated) (Kingslake calls it a reverse Tessar, says it isn't an echt tessar type) that came with my little Speed Graphic.

    All of which points to what is probably the right answer to the OP's question, viz., that design type isn't always a good predictor of how well a lens that conforms to the type will perform. The prescription matters. When Usenet's rec.photo groups were active, Richard Knoppow made the point repeatedly that the computations that led to Wollensak's latest tessar type Raptar contained an error; the design was poorly corrected for coma, had to be stopped down more (two stops more, he said) than the comparable tessar type Ektar to match the Ektar's image quality in the corners. Build quality matters. And, for elderly used lenses, condition matters.

  6. #16

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    Re: f/4.5 Tessars

    Quote Originally Posted by IanG View Post
    It was a better lens Dan, after the outbreak of WWI the scenario changed and Ross no longer paid Zeiss any Royalties for the patents. I've an Air Ministry 141mm EWA f18 Ross lens that'sn clearly the same as the Ross Zeiss f16 Protar.

    Reality is some Xenars are 5 element yet they all classed as Tessars, many Xpres lenses are 5 element and some are Tessars, as Ross had taken over Zeiss in the UK (Mill MillHill) during WW1 , there were no issues with getting around Patents, Germany was in ruins.

    Ian
    But then you have for instance the American Gundlach Radar, a 5 element lens made to get around the Tessar patent.
    One man's Mede is another man's Persian.

  7. #17

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    Re: f/4.5 Tessars

    Quote Originally Posted by E. von Hoegh View Post
    But then you have for instance the American Gundlach Radar, a 5 element lens made to get around the Tessar patent.
    ... and what a sweet lens that is!

  8. #18
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    Re: f/4.5 Tessars

    Quote Originally Posted by Dan Fromm View Post
    Ian, what do Protars have to do with Tessars?
    Both were Zeiss lenses made under licence by Ross, but Ross stopped paying Royalties and continued making the EWA Protar without the name during and after WWI.

    Quote Originally Posted by Dan Fromm View Post
    Why do you say that the Xpres, any version, is better than the Tessar, any version? I ask because I have a Selfix 820 with the renowned 105/3.8 Xpres. I've never got a satisfactorily sharp shot with the wretched thing. I've checked, the lens is properly collimated. And I've checked, the lens' rear group is a doublet, not a triplet, so it is an echt tessar type.
    I didn't say every version, rather Xpres lenses in general, actually the Xpres on the Selfix is unusual because it's cell focussing and not a Large format lens, I have two and both mine are very sharp, you must be unlucky with yours.

    The Xpres on my Microcord is better than the Tessars or Xenars on Rolleiflex's and a touch sharper than my Yashicamat 124 at wider apertures, this matches magazine test repots but from practical experience. Stopped down there's nothing between thase lenses and moderm plasmats i practical use.

    I've had some very poor lenses over the years and from supposedly good manufacturers, so there can be the odd poor samples, none were Teassar type

    Quote Originally Posted by Dan Fromm View Post
    All of which points to what is probably the right answer to the OP's question, viz., that design type isn't always a good predictor of how well a lens that conforms to the type will perform. The prescription matters. When Usenet's rec.photo groups were active, Richard Knoppow made the point repeatedly that the computations that led to Wollensak's latest tessar type Raptar contained an error; the design was poorly corrected for coma, had to be stopped down more (two stops more, he said) than the comparable tessar type Ektar to match the Ektar's image quality in the corners. Build quality matters. And, for elderly used lenses, condition matters.
    Same goes for CZJ Tessars after WWII when specialist optical glass was hard to obtain by CZJ and lenses were constantly being re-computed by hand to suit teh available glasses..

    Ian

  9. #19

    Re: f/4.5 Tessars

    The Rodenstock Ysarex that came on the Polaroid 110 cameras is an excellent Tessar. Coverage is bare, but it has a unique tonality.

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