Simple Frage zum Apo-Telyt-M 135mm f/3.4

[onkelpi]

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Handel es sich bei diesem Objektiv bei der optischen Rechnung um ein Retrofokus-Design?

Und wäre das beim Elmarit-M 90mm f/2.8 ebenfalls der Fall?

Bin da etwas unbeschlagen. Bei einigen Leica-M-Weitwinkel-Objektiven lässt sich das recherchieren z. B. bei Herrn Rockwell.

Danke für Eure Hilfe 😉

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[zeitz]

Retrofocus designs are for wide angle lenses (less than 50mm), particularly on SLRs where the mirror limits how close the rear element can be to the focal plane.  So the 135 Apo Telyt and the 90 Elmarit-M are in no way retrofocus designs.  

Modern lens designs, which use special glass and aspheric elements, also can deviate significantly from the classic lens layouts.

Regarding telephoto lenses, such as the Elmarit and Apo-Telyt, most designs are evolutions of Ernostar and Sonnar layouts.  This is not true of Elmars which are evolutions of Tessars and tend to be long focus lenses rather than true telephotos.  Tele-Elmars are true telephotos.  The 135mm f4.0 Elmar and the 135 f4.0 Tele-Elmar are totally different designs.  True telephotos have a physical length that is shorter than the optical length.  Long focus lenses have physical and optical lengths that are essentially the same.

Ken Rockwell is wrong as much as he is right.  My recommendation is just pick the Leica lens with the focal length and aperture you like and don't be concerned about about design or someone's review.  If Leica was happy enough to sell the lens, you will be happy when you use it.

 

[Robert Blanko]

Alright, that‘s essentially what I was about to write when I saw the reply. The 135 apo telyt as well as the 90 2.8 elmarit use a so-called tele lens design which allows keeping the lens shorter than its nominal focal length.

The retro focus Design on the other hand essentially  causes the opposite - allowing a lens having a length larger than the nominal focal length, for instance to allow a swinging mirror in the optical path.

Sometimes the latter Design is also referred to as inverse tele design.
 

Thus, the short answer is „no“ - oder auf Deutsch „nein“. 😏

Edited December 2, 2020 by Robert Blanko

[onkelpi]

Thank you for your quick and very informative reply. Didn't realized, i surfed the International Forum 🤗