Zeiss T* coatings - what and when?

Discussion in 'Medium Format' started by peter_yardley, Jun 7, 2006.

  1. Any Zeiss/Optics experts out there?

    I'm interested to know when T* coating appeared on Zeiss lenses, and what is
    supposed to be so special about it?

    obviously they had coated lenses before, single then multi coated, and then they
    must have branded this multi coating T* - but when was this (1978? 1982?) and
    what does it amount to?

    I've heard some hassleblad experts say the multi coated chrome lenses were the
    ultimate from Zeiss (rather than the later black finish ones). Is there any
    basis for this, or is is just Quality Control reaching its peak in the late 70's
    and going down slightly in the 80's?

  2. From what I have found the first T ('Transparent') coating was developed in 1935. It allowed light transmission of 80% compared to uncoated lenses. This led to further development for the military during the war (the NR coating). The T* coating (which was an improved T coating and transmitted 90% of the light passing through it) appeared in 1990.

  3. It is the same as multi-coating used by other brands. It reduces flare and improves contrast.
  4. Here's my understanding of the T* coatings. T* coatings were introduced in the fall 1972 with no fanfare. It was Zeiss's multicoating process. In 1974 Zeiss started marketing "T*" as a reaction Pentax's SMC (Super Multi Coated) lens ads.

    Chrome Hasselblad lenses made in late 72 and 73 are T* though not marked. Early black C lenses are T* but not marked. My understanding is that in late 73/early 74 Zeiss started marking Hasselblad lenses as "T*". There are chrome C lenses that are marked T*. I have only seen this on a 80mm lens.

    In 1982 while I was in Germany I spoke with the Zeiss factory about my chrome 250 Sonnar. I was told that it was a 1973 vintage lens and it was T* coated but not marked as such.
  5. Yeah, it all goes down to Pentax's decision to come out and declare their multicoating as a
    big deal. I was talking to our local Leica rep (who is German from Wetzlar and has worked
    there 30 years) that Leitz was using multicoating on certain lenses since the 40s, but it never
    occurred to them to tell anyway. He chalked it up to the general tendency of the Japanese
    companies to be much better at marketing innovation, while the older German mentality was
    to let the products speak for themselves. For better or for worse, products don't always speak
    for themselves, even if they are better... (see VHS winning over Beta etc). I am not trying to
    argue that German products or better or anything like that, just that their method of
    marketing was different, and multicoating was one of the areas where this came to the fore.
  6. "tell anyway" should be tell ANYONE...sorry.
  7. The reason that Zeis refers to its coatings as T* is related to its cinema and movie film lenses. The advent of the coating called T* was the first time that a movie lens could be made where the mathematical aperture F number was the same as the actual light transmission T stop. From the introduction of the T* coating the losses through the glass were reduced almost to zero and T stops and F numbers became almost interchangeable. I say almost because for really critical exposure matching T stops are still used.

    The history of Zeiss inovations and improvements tends to be a gradual process without a lot of marketing hype to push the change. that is why there are some T* lenses still marked as T. In much tghe same way that there are some Hasselblad 500 series cameras with older model identification marks than the actual camera would suggest. I.E the new model with an old badge on it
  8. thank you for some very interesting information and answers.

    I have an LF Zeiss Planar from the 70's that looks multi coated, but isn't branded T*. it is serial # 5793860 - is there a way to find out its date of manufacture?
  9. Peter, per the Vade Mecum 1969-'71. For a narrower range of dates, find a kind person who has a copy of Hartmut Thiele's list, based on Zeiss factory production records. Or buy one y'rself. Not a multicoated lens.
  10. Thanks to someone who does own the Thiele book, for their off list contact. It is actually 1975 production, and is multicoated, but not T* branded.

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