Ziess Biogon 21 f/4.5 and CV 21 f/4 - the same lens!

Discussion in 'Leica and Rangefinders' started by andrew robertson, Aug 7, 2009.

  1. Have a look at the lens formulae with these two.
    The CV's formula is visible here: http://www.cosina.co.jp/seihin/voigt/english/s-wide-e.html
    The CZ's formula is visible here: http://www.zeiss.com/C12567A8003B8B6F/GraphikTitelIntern/CBiogonT45-21ZM_1/$File/linsenschnitt.jpg
    Element 6 looks a tiny bit different on these drawings, but I don't think the lens formulae given in advertising material are always engineering grade.
    Anybody that has both willing to post an A/B of the two?
  2. The number of elements and their groupings look the same, but the convexity and thickness of the elements look different.
  3. Well, correct me if I am wrong, but don't they have to be different if they have different lens speeds? Unless of course the Zeiss one is leaving the iris partially closed at its widest setting...but I would say that you cannot really determine it is identical unless you have more detailed optical diagrams, preferably with measurements.
  4. Hi Stuart, I think they do look different. Having said that, I also think two lenses can be the same even though they have different rated speeds ... unusual, but possible. For instance, there are those who swear that the 21mm f3.4 Super Angulon is a half stop slow at every stop ... which effectively makes it more like a 21mm f4 Super Angulon speed-wise, at least wide open.
  5. They are both 8 element Biogon formulations. They are both made in the Cosina factory. But I would very seriously doubt they are the same lens. I would bet the farm there is a difference in the glass, the coating, and the tolerances.
    Does that justify the 3x difference in price? To some it does, to some it does not.
    I have the CV 21 in LTM. It is a great lens. But I suspect the Zeiss one is a bit better.
    I have several Zeiss lenses (assembled in the Cosina factory) as well as several CV lenses. I can assure you there is a difference.
  6. I borrowed a screw mount CV 21 for a few weeks, and now have the Zeiss C Biogen 4.5/21. I agree with Sean Reid's assessment that the Zeiss is sharper and renders higher contrast. Quite a nice lens~ to me it has a more interesting character than the CV. The Zeiss has a really nice bite with Tri-X. Can be good on the M8 too, but exposure and processing is more critical on that camera in certain situations under harsh lighting conditions.
  7. [​IMG]
    Zeiss 4.5 w/M8
  8. [​IMG]
    Zeiss w/Tri-X
  9. No. they're not the same lens. You and a chimpanzee share 95% of your DNA, but you're not a chimp, are you?
    The CV 21 is based on a Biogon formula, but even small differences between different elements reflect different design compromises and make it a different lens.
    I've owned the CV, it was a great lens for the price, but I did notice significant barrel distortion. The Zeiss Biogon 21/4.5, from reports, features next to none, and makes it a great choice for architecture, a subject I wouldn't want to tackle with the CV - which is of course amazing value for money, and recommended if you don't use that FL too often.
  10. Hi Andrew
    The third, fifth and sixth elements look different to me.
    I have the CV lens, and I'm very happy with it. I almost certainly won't try to get the Zeiss lens....

  11. Ray, have you done a side by side in the same light?
    Good light can make a bad lens look great, and bad light can make a great lens look crappy.
    If there is anybody who owns both, an A/B would probably put my mind at ease!
  12. Of course, the Cosina lens does not have T* coating technology.
  13. "Of course, the Cosina lens does not have T* coating technology."
    It may have the same coating, but Cosina may not be able to advertise it as "T*", which was originally Pentax technology in any event.
  14. I seem to remember reading that the lens elements in the Zeiss lens come from the Zeiss factory in Germany. I am sure the elements in the CV lens come from some quality lens grinding factory in the orient somewhere.
    To say the lenses are the same is to say that the V-8 in your plumber's work truck is the same as the V-8 in a NASCAR Nextel Cup car. However they both will get you from point A to point B.
    Now, I will say that my CV 21mm lens is very good. But I would never believe it is as good as the Zeiss lens. Glass counts in optics.
  15. I've owned and tested both. The ZM offering is a bit sharper with higher contrast and less flare tendency. In fact I think it's technically the sharpest lens I've ever owned, easily exceeding 100 lp/mm on resolution charts. Performance is near peak at f/4.5 except for slight fall off in the corners. I liked the ZM so much that I wound up selling my 24/2.8 Elmarit-M and now ony use the 21/4.5 as my super wide M lens. The CV is a great buy for the money but the ZM is in a different class.
  16. Erwin Puts gives the 21/4.5 Zeiss-M (ZM) and the 21/4.0 CV (Cosina-Voigtlander) high ratings. He writes that the VC 21mm is slightly sharper than the 21SA and has modern coatings. Of interest to some shooters, me included, are three other factors: 1) the CV is smaller/lighter and therefore more likely to go into the bag on a trip, 2) the 21 CV is f/4.0, while the 21 ZM is f/4.5 -- ZM tiny bit slower, 3) I cant see myself investing $900+/- for a super-wide I dont use alot.

    In summation, the CV 21mm/4.0 is smaller, lighter, less expensive and more likely to become part of my travelling arsenal. However, if you're a big time super-wide shooter than by all means consider the 21/4.5 ZM as its one of the sharpest out there. Regards - Paul

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